
Class 
Book. 



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.XlL 



Copyright N". 

COPYRIGHT DEPOSIT. 



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V 



THE 



PRINCIPLES 
of MANURING 

^ An Application of Chemistry to Agriculture ^ 




ALFRED VIVIAN 

College of Agriculture 
Ohio State University 



Reprinted from THE NORTH AMERICAN FARMER 



^f> 



tf 



I Oop>ficnv gntry i \\^ 

COPY a. I 



THIS little pamphlet pretends to be no more than it is, 
a reprint of aseries of news paper articles Ti'urriedly 
written during the stress of college work. The subject 
of the nutrition of plants is so large that each phase 
of it could of necessity be only very briefly considered in 
space available, and the writer did not attempt to make the 
discussion of any subject exhaustive. For this reason 
many things have been omitted that might be discussed 
with profit in a larger work. Only the more important 
considerations concerning the maintenance of fertHily have 
been presented, but it is believed that the statements so far 
as they go are in accord with the best scientific thought 
and practice of the day. 

A large number of typographical errors will be found 
in the text, as the manner in which this pamphlet was 
printed made it impossible to have the proof read and 
corrected. It is believed, however, that the errors are not 
such that they will hide the meaning in any case, and the 
indulgence of the reader is asked for these as well as for 
the other imperfections of the text. 



Copyrighted l'>04 

Cott's Qdick Printinc, HOt^SK 
Columbus, Ohio 



/ 



-^ 



THE PRINCIPLES OF MANURING 

An Application of Chemistry to Agriculture 



Z^- 



'^i^ji:iJ7 



PART 1. Plant Food hi General. Its Nature and Source. 



J> ^ iP- 



FARMING is a business, and the suc- 
cessful farmer must be, first of all, a 
businessman. He follows his avoca- 
tion, primarily, for the money he can 
make, and like other business men 
Dims to get the greatest possible re- 
turn for the money and labor involved. 
It is not enough to produce crops, but 
they must be so produced as to yield 
a profit on the capital invested. To 
succeed he must be thoroughly ac- 
quainted with every detail of his occu- 
pation and must strive to stop all 
leaks and prevent needless waste. At 
the same time, he must bear in mind 
that it is a good business principle to 
spend a dollar vhenever he can see 
that it Mill come back to him with 
interest. 

Agriculture differs fmm mercantile 
pursuits in being not merely a busi- 
ness, but an art '■i>: v/ell — the art of 
producing plants and animals that are 
useful to man. To -jnderstand this art 
necessitates a knowledge of the prin- 
ciples upon which the art of agricul- 
ture is founded (sucti, for example, as 
geology, chemistry, botany, physics 
and others which might be men- 
tioned), and an understanding of these 
principles is essential to an intelligent 
and rational practice. A few years 
since "anyone could be a farmer." It 
was only necessary to sow and reap, 
for Nature dealt lavishly with man 
and gave to him freely of the fertility 
she had been storing up for countless 
ages. A system of extravagant and 
unbusincss-like farming, however, has 
so impoverished the soil, in some 
parts of our country, that many farms 
are already abandoned, having ceased 
to be profitable, and that, too, in lo- 



calities where the land once com- 
manded high prices. This fact is the 
more lamentable because the exhaus- 
tion of the soil might have been pre- 
vented by an intelligent foresight on 
the part of our earlier farmers. 

Chemistry has done much to ex- 
plain how the fertility of the land 
may be conserved, and it is the aim of 
this short treatise to present, as 
briefly as possible, the latest views of 
agricultural chemists and farmers on 
Ihis important subject. The intention 
is to make the series thoroughly prac- 
tical, and for this reason the minimum 
of theory and the maximum of dem- 
onstrated facts will be given, and all 
technically chemical language will be 
avoided when possible. Before taking 
up the subject of manures and ferti- 
lizers it is deemed desirable to devote 
a short time to the consideration of 
plant food in general — v/hat it is and 
from whence it comes. 

Plants of First importance to 'he 
Farmer. — A.11 agricukure depends on 
the growth of plants and consequently 
the profit that accrues to the farmer 
depends, primarily, upon the value of 
the crops his farm produces. In some 
styles of farming the profit comes 
from the sale of crops that are useful 
in providing food, fuel or raiment for 
man, while in others the direct gain 
ccmes from the sale of animals or 
animal products. Even in the latter 
case the feeding crops that can be 
grown on the farm determine its earn- 
ing power, for the sale of animal 
products is simply an indirect method 
of marketing the crops. 

The profit from the farm is depend- 
ent not only upon the total crop pro- 
duced, but also, and to perhaps a still 
larger degree, on the yield per acre. 
It stands to reason that if the crops 
now produced on two hundred acre? 



could be grown on one hundred, the 
returns would be greater, providod the 
labor and other nost involved were 
not materially increa.sod, for in the 
latter case the interest on the money 
invested in one hundred acres of land 
would be clear gain. On the other 
hand it is apparent that nothing is 
gained by increased production per 
acre if the larger crop is obtained at 
a total expenditure in excess of that 
required for the smaller yield. As a 
matter of *acc our most succes^.sful 
farmers have demonstrated that the 
present average of crops can be dou- 
bled and at a cost per acre scarcely 
more than is now required for the 
half crop. To accomplish this leces- 
sitates a bioader knowledge of the 
food requiiements of plants than is 
posse.s^ed by the majority of our farm- 
ers. This knowledge being fundamen- 
tal, it seeni.s strange that more atten- 
tion has n"^* been devoted to this sub- 
ject by those vitally irterested. 
Strange as it may seem, it is a fact 
that, while he has reasonably clear 
ideas on foods for animals, the aver- 
age agriculturist has only very vague 
and often unfounded notions on the 
subject of plant food and plant nut i- 
tion. A thorough understardin.'? of 
these subjects on the part of our fore- 
runners in agriculture would have ren- 
dered it unnecessary to feel concerned 
regarding the matter considered under 
the next heading. 

(2) Exhaustion of the Soil. — It is a 
matter of common experience that 
continued cropping results in a loss of 
fertility. The experience of the East 
teaches some lessons by which the 
West may profit. In the beginning the 
productiveness of the rich virgin soil 
seemed unlimited. For years large 
crops were produced with apparently 
no decrease of fertility. Sooner or 
later, however, the crops Degan to di- 
minish in size, gradually to be sure, 
but unceasingly, until at last the yield 
became so small that it no longer paid 
for the cost and labor of cultivation. 
This state of affiairs came about more 
rapidly if the same crop was grown 
continuously on the same field, as was 
often done with wheat. The soil was 
now said to be exhausted and the 
farms were abandoned. An exhausted 
soil in this sense means one that will 
no longer yield profitable returns, and 
not necessarily one that will produce 
no crop. As a matter of fact a soil 
cajinot become exhausted, if by ex- 



haustion we mean total inability to 
produce a crop. 

At the experiment station at Rot- 
hamsted, England, barley grown con- 
tinuously on the same plot for forty- 
three years without the use of fertiliz- 
ers of any kind yielded in the forty- 
third year ten (10) bushels of dressed 
grain per acre; the average for the 
last eight years being eleven and 
three-fourths (11%) bushels. Wheat 
grown in the same way for fifty years 
produced in the fiftieth years nine and 
three-fourths (9% bushels of grain 
per acre; the average for the last 
eight years being eleven and one-half 
(11%) bushels. In these cases the 
soil seems capable of keeping up this 
yield indefinitely, for the average for 
the last twenty years is practically 
the same as the average given above 
for the last eight years. 

While these facts indicate that the 
soil can never be comj^letely exhaust- 
ed, it is exhausted to all practical pur- 
poses, when the crop produced ceases 
to be profitable. The first question 
that naturally suggasts itself is — Why 
does the productive power of the soil 
diminish? 

(3) The Plant Removes Something 
From the Soil.^It is evident that the 
virgin soils must have contained large 
quantities of some substance or sub- 
stances that were necessary to vigor- 
ous plant growth and that these ma- 
terials were removed from the soil 
when the crop was harvested. It is 
not possible to explain the rapid de- 
crease in fertility on any other basis, 
for it seems to be to a certain extent 
independent of any changes in cli- 
matic conditions. The change in the 
mechanical conditions of the soil has 
been suggested as a possible explana- 
tion for its decreased productive 
power, but even this does not fully ex- 
plain it. It is apparent, also, that 
plants vary in their power to extract 
these substances from the soil, for it 
is well known that a soil may be ster- 
ile towards one class of plants and 
still poduce a luxuriant growth of an- 
other. To ascertain what these ma- 
terials are that the plant removes from 
the soil, it is necessary to analyze the 
plant and then to determine the 
sources of the ingredients found. For 
the purpose of this study the corn or 
maize plant is chosen, as it is perhaps 
the most important of all plants to the 
American farmer. Before st'^ting the 
analysis, it is advisable to devote a 



moment to a few preliminary consid- 
erations. 

(4) Elements and Compounds. — 

Chemistry teaciies that all matter is 
composed of simple substances called 
elements. Between seventy and 

eighty of them are known. They are 
called elements because they are 
the simplest substances known and 
cannot, by any means yet discovered, 
be separated into simpler or different 
substances. Iron, gold, silver and sul- 
phur are examples of elements. Two 
others, both gases (i. e., oxygen and 
nitrogen) make up the bulk of the 
air. 

Most materials with which we are 
familiar are complex bodies and com- 
binations of two or more elements. 
Such bodies are called compounds. 
While the number of elements is 
small, there are many thousands of 
compounds. This is due to the fact 
that the same elements can combine 
in many different ways, each combina- 
tion forming a different compound. 
Alcohol, sugar, starch and acetic acid, 
for example, are substances very un- 
like in their properties, and yet all 
consist of the three elements, carbon, 
hydrogen and oxygen, though these 
elements are present in different pro- 
portions. Plants are composed of a 
large number of compounds and an 
ideal analysis would first separate the 
plant into its compounds and then 
these compounds into the elements of 



which they are composed. Approxi- 
mately such an analysis can be made. 

(5) Chemical Composition of the 
Corn Plant. — If a quantity of green 
corn is allowed to wilt in the sun it 
loses a large percentage of its weight, 
due to the evaporation of the water 
which it contains. If the remainder 
is now heated in an oven at 212 de- 
grees F. it again decreases in weight, 
but finally reaches a point where the 
weight does not change, because all 
the water is now driven off. Water is 
composed of the two elements, hydro- 
gen and oxygen. What remains after 
expelling the water is called the dry 
matter of the plant. The dry matter 
burns on being ignited and a very 
small ?.mount of mineral matter re- 
m.ains which is called ash. The part 
that burned and completely disap- 
peared is known as organic matter. 
The organic matter is composed of 
four classes of compounds known as 
proteins, fats (ether extract), crude 
fiber and carbohydrates (nitrogen free 
extract), and these compounds in turn 
are made up of the four elements, car- 
bon, oxygen, hydrogen and nitrogen. 
The ash contains the elements chlor- 
ine, potassium, phosphorus, calcium, 
magnesium, ii'on, sulphur, sodium and 
silicon. The following table shows 
the ingredients found in one thousand 
pounds of the matured corn plant, i. e., 
when the plant is in condition to be 
cut for shocking: 



COMPOSITION OF THE CORN PLANT. 



Corn Plant 
leOO lbs. 



Water J Hydrogen 88.1 
793 / Oxyyeii 704.9 



Dry I 

Matter { 

307 



Organic 

Matter 

195 



f Proteia 18. 

) Fat 5. 

1 Fil)er SO. 

I Carbohydrates 12- 



r Ni troy en 2.9 
! Carbon 90.5 
'1 Oxvi^-^en SS-9 
I Hydrogen 12 7 



f Chlorine 0.4 
I Potash 4.0 

Phosphoric Acid 1.2 
I Lime 1.6 
Ash 12 i Majj-nesia 1.4 

Iron Oxide 0.3 

Sulphuric Acid 0.3 

Soda 4 
L Silica 24 

(NoTK.— All of the elements nieutioned above as occurring in the ash, with the ex- 
ception of clilorine, are combined with oxyffen. In the table the names under "ash" 
represent these combinations, i. e. potash is composed of potassium and oxyyen: phos- 
phoric acid is phosphorus and oxygen; lime is calcium and oxygen, etc ) 



From what has been said it will be 
seen that of the elements known, only 
thirteen (13) are found in plants, for 
what is true of the corn plant holds 
true of all other plants. It will be 
shown that of this number, three are 



probably not necessary to plant 
growth, leaving only ten elements that 
are essential. The table shows that 
three elements (i. e., hydrogen, oxygen 
and carbon) make up ninety-eight and 
one-half (98i/^) per cent of the entire 



composition of the plant, the remain- 
ing elements constituting only one 
and one-half (1%) per cent. 

(6) Importance of Water to the 
Plant. — One of the most striking points 
brought out by the chemical analysis 
is the large proportion of water that 
enters into the composition of the 
plant. A reference to the table shows 
that nearly eight hundred (800) of the 
one thousand (1,000) pounds of the 
matured corn plant consist of water 
in a form that can be driven off at a 
heat not above the boiling point. In 
the organic matter is found 12.7 
pounds of hydrogen and 88.9 pounds 
of oxygen, which practically all came 
originally from water, making a total 
of nearly 900 pounds derived from this 
source. These figures represent but 
a small part of the water actually re- 
quired by the crop. Experiments 
have shown that approximately 300 
pounds of water passes through the 
plant for each pound of dry matter 
produced, so that 1,000 pounds of corn 
uses at least 30 tons of water during 
its growing period. As this quantity 
of corn can be raised on one-thirtieth 
of an acre, it follows that to mature 
an acre of corn the crop must be sup- 
Ipied with 900 tons of water, or a 
quantity that would make a layer over 
the acre eight inches deep. 

This, again, takes no account of the 
amount of water lost from the soil by 
percolation or drainage. It has been 
estimated that this quantity is at least 
equal to that used by vegetation, so 
that one acre of corn probably re- 
quires a precipitation of at least 1,800 
tons of water. These statements show 
clearly the necessity of carefully con- 
serving the moisture of the soil, a 
point that cannot be too strongly em- 
phasized. 

The water all enters the plant at 
its roots, being absorbed from the soil, 
and all but a small part of it is given 
off from the leaves by evaporation or 
transpiration. Water is important to 
the plant in several different ways. It 
is, first of all, the most important food 
of the plant — in the sense that it sup- 
plies the matter composing almost 
nine-tenths of the weight of the plant. 
It is also necessary to enable the 
other food in the soil to enter the plant 
as these materials can be absorbed by 
the plant only when they are in solu- 
tion. 

Water is needed to give stiffness or 
rigidity to the more succulent parts of 



the plant, as is shown by the droop- 
ing of plants when the supply of water 
is insufficient. It is probable that 
water performs an important function 
in controlling the temperature of the 
plant. The chemical processes in the 
plant cells produce heat and the ex- 
cess of heat is removed by transpira- 
tion of water through the leaves, just 
as it is removed from our bodies by 
the transpiration (perspiration so 
called) through the skin. 

So important to vegetation is the 
water supply that some investigators 
claim that the question of fertility is 
wholly one of having present in the 
ground the proper amount of moisture 
and is independent of the chemical 
composition of the soil, except as this 
composition affects its power to fur- 
nish the plant with water. This view 
is undoubtedly extreme and is not gen- 
erally accepted. There is no doubt, 
however, that the proper condition of 
moisture is the most important factor 
in determining the fertility of the land, 
and that more soils fail to produce 
good crops for lack of it than for any 
other cause. In few cases is the water 
supply sufiicient to produce the maxi- 
mum crop of which the soil is capa- 
ble. 

(7) Part of the Oxygen From the 
Air. — A small quantity of the oxygen 
in the plant probably comes from the 
air. One-fifth the volume of the air 
is oxygen and the plant uses this to 
some extent. Plants breathe in much 
the same manner that animals do, for 
all cells must have a supply of oxygen 
in order to live. The oxygen of the 
air combines with the materials in the 
cells, one of the results being the pro- 
duction of heat, just as the oxidation 
taking place in the animal body pro- 
duces heat. That heat is evolved by 
the living vegetable cell can easily be 
proven experimentally by confining the 
plant in such a way as to prevent ra- 
diation. The rapid heating of silage 
during the filling of the silo is doubt- 
less due to the breathing process of 
the cell, the heat in this case being 
unable to escape. 

(8) Carbon in Plants Derived From 
the Air. — Nearly one-half of the dry 
matter in the plant consists of the 
element carbon, all of which is de- 
rived from the carbonic acid gas that 
constitutes about four-hundredths of 
one por cent of the volume of the at- 
mospl'.ere, or about ons part in ten 



thousand. Carbonic acid gas is a 
compound of the elements carbon and 
oxygen. Green plants have the power 
to decompose this gas, retaining the 
carbon, and setting free the oxygen. 
This process is known as the "fixa- 
tion (sometimes assimilation) of 
carbon," and takes place principally 
in the leaves. The power to fix car- 
bon is dependent in some way on the 
presence of the green coloring matter 
(chlorophyll), so that it is only those 
plants having green leaves that can 
use the carbonic acid. Such plants as 
mushrooms and other fungi, for in- 
stance, cannot obtain their carbon in 
this manner, but must procure it 
through the decomposition of organic 
matter, or. in other words, must have 
their food previously prepared for 
them. Green plants, on the other 
hand, can manufacture their own food 
from the inorganic materials of the 
soil and the atmosphere. 

(9.) Sunlight Necessary to Carbon 
Fixation. — The decomposition of car- 
bonic acid by the plant, and the assim- 
ilation of the carbon, takes place only 
during the daytime. A certain amount 
of energy is necessary to break apart 
the carbon and oxygen of carbonic 
acid and this energy is furnished by 
the sunlight. The stronger the light 
the faster the fixation of carbon, 
which explains the commonly observed 
fact that most plants grow more vig- 
orously in full sunlight than in shade 
or diffused light. The plant has not 
power to use carbonic acid in the ab- 
sence of light, so that this process 
ceases during the night. 

It is well known that seeds will 
germinate in the dark and produce a 
feeble, spindling growth of pale foli- 
age, but that the plants so produced 
soon cease to develop. Such plants 
grow until they exhaust the food 
stored in the seed, but have no power 
to use the food in the air and soil, and 
analysis shows that the plant con- 
tains less dry matter than was present 
in the seed. 

In the presence of light, however, 
the plant absorbs the carbonic acid 
of the air and causes the carbon to 
combine with the water and other 
substances taken in through its roots, 
to form carbohydrates, proteids and 
other complex compounds of which 
the plant is composed. It is now gen- 
erally believed that the green plants 
derive their carbon solely from the 



carbonic acid of the atmosphere and 
are not dependent in any way upon 
the carbonaceous matter in the soil; 
in fact, that they are incapable of 
using carbon except in the form of 
carbonic acid gas. 

Numerous experiments have proven 
that the supply of carbon in the air is 
ample for the largest crops. To be 
sure, in certain pot experiments a 
larger yield was obtained by increas- 
ing the carbonic acid in the air, but 
under field conditions the yield is lim- 
ited by other factors and never by the 
supply of carbon. 

All processes of fermentation or de- 
cay, all burning and the breathing of 
animals, combine to return carbonic 
acid to the air as fast as it is removed 
by growing plants, consequently the 
amount of this gas in the atmosphere 
remains constant. In all probability 
that now present in the air has been 
many times built up into organic mat- 
ter only to be again set free by its 
decomposition. 

(10) Carbon Costs the Farmer 
Nothing. — The point of practical im- 
portance brought out by this study of 
the fixation of carbon is that the car- 
bon is furnished free of cost. In other 
words the carbonaceous matter pro- 
duced in the crop results in no im- 
poverishment of the soil. There is no 
need then, of supplying strictly car- 
bonaceous manure to the field, as the 
crop does not use the carbon in the 
soil. It will be shown later that such 
manures may indirectly be beneficial 
to the plant. 

(11) The Nitrogen Problem. — A ref- 
erence to the table given in section 5 
shows that only about one and one- 
half (1%) per cent of the dry matter 
of the corn plant consists of nitrogen. 
Some plants contain more nitrogen 
than this, but the amount rarely 
equals three per cent of the dry mat- 
ter or six-tenths of one per cent of 
the green plant. In spite of the small 
quantity of nitrogen in the crop it is 
the most important of all plant foods 
from the practical point of view. In 
fact, the solution of the problem of the 
maintenace of fertility depends upon 
an economical method of conserving 
and renewing the nitrogen supply of 
the soil. This does not imply that it 
is more necessary to vegetation than 
are the other constituents, but that it 
is the most expensive element to fur- 



nish by means of fertilizers and is 
also, unfortunately, the element most 
easily lost and wasted. 

(12) The Nitrogen of Plants Comes 
From the Soil. — Most of the crops 
raised by the farmer are entirely de- 
pendent on the soil for their supply of 
nitrogen. Most of the nitrogen pres- 
ent in the soil is locked up in the in- 
soluble organic matter and in this 
form is not available to plants. 

Some of the nitrogen exists in sim- 
ple compounds called nitrates, which 
consist of nitric acid combined with 
one of the mineral elements of the 
soil. The majority of farm crops can 
use only that part of the nitrogen in 
the soil that is present as nitrates, 
so that so far as the nitrogen is con- 
cerned the fertility of the soil depends 
on its nitrate content. The nitrate 
present in the soil at any one time is 
exceedingly small, but, under proper 
conditions, the supply may be re- 
newed with sufficient rapidity to meet 
the needs of the plant. 

(13) Source of the Nitrogen of the 
Soil. — A small part of the nitrogen in 
the soil is derived directly from the 
atmosphere. Minute traces of am- 
monia (a compound of nitrogen and 
hydrogen) are always found in air 
and during electrical storms small 
quantities of the nitrogen and oxygen 
in the atmosphere are combined to 
form nitric acid. These substances 
are dissolved in the rain water dur- 
ing showers and are carried into the 
soil. The quantity received by the 
soil from this source is very small, 
amounting only to from six to eight 
pounds per acre per year, the maxi- 
mum amount being less than one- 
tenth that required by a crop of corn. 
Nearly all of the nitrogen in the soil 
is present in the more or less decayed 
organic matter left behind by the 
plants that it has previously produced. 
Plants build up the nitrogen into com- 
plex protein compounds and, under 
natural conditions, when they die 
these substances, in connection with 
the other constituents of the plant, 
become a part of the soil. As long as 
the nitrogen remains in this form it 
is of no value to the new generation 
of plants, for the organic matter must 
first be decomposed and the nitrogen 
changed into the form of nitrates. 

(14) Nitrification. — The soil must 
not be regarded as an inert mass of 



mineral matter and refuse of former 
plant growth. It is, in fact, an im- 
mense laboratory in which millions 
of tiny workmen are bringing about 
marvelous chemical changes. The 
principal factors concerned in these 
transformations are bacteria, of 
which, it is estimated, there are pres- 
ent in the neighborhood of one hun- 
dred fifty millions in each ounce of 
surface soil. Some of these bacteria 
cause the fermentations and decay 
that return the carbonic acid to the 
air. Others, and these are of partic- 
ular interest here, bring about the de- 
composition of the nitrogenous or- 
ganic matter with the ultimate pro- 
duction of nitrates. 

The transformation of organic ni- 
trogen into nitrates undoubtedly re- 
sults from the action of more than one 
species of bacteria and takes place in 
three or more different steps. The 
organisms necessary to produce these 
changes are ordinarily present in all 
soils. Nitrification takes place only 
when the temperature is more than 
five degrees above freezing and be- 
comes more rapid with rise of tem- 
perature. Hence, it ceases during the 
winter months and is most vigorous 
during the hot months of midsummer. 
The nitrifying bacteria cannot live 
without a sufficient supply of oxygen, 
for this reason stirring the soil in- 
creases the rate of nitrification. The 
nitrifying bacteria cannot thrive in a 
soil that is acid, so that the presence 
of carbonate of lime or some other 
substance that will neutralize any 
acid produced in the soil is essential 
to nitrification. All of these points 
will be discussed in greater detail later, 
for the present it is sufficient to em- 
phasize the importance of the process 
of nitrification to the growing crop. 
So vital, indeed, is the subject, that 
successful agriculture may be said to 
depend largely on providing proper 
conditions for rapid nitrification. 

(15) Denitrification. — While the ni- 
trifying bacteria may be said to be the 
farmer's friends, there are, unfortun- 
ately, in the soil other organisms that 
produce evil results. One class of 
these, known as denitrifying bacteria, 
decompose the nitrates, and perhaps 
some other nitrogenous compounds, 
with the final result that the nitrogen 
is set free and returned to the air in 
its elemental condition. This process, 
of course, robs the soil of a part of its 



nitrogen and is especially unfortunate 
in that it removes the part that was 
most available to the crop. The con- 
ditions that are prejudicial to nitrifi- 
cation (i. e., lack of oxygen and pres- 
ence of acidity) are those that favor 
denitrification, so that the farmer in 
producing proper conditions for the 
former desirable process is at the 
same time preventing the injurious 
denitrification. 

(16) Can Plants Use Free Nitrogen 
of the Air? — About four-fifths of the 
volume of the air consists of the ele- 
ment nitrogen, so that if this was gen- 
erally available to plants, there could 
be no such thing as "nitrogen starva- 
tion." Perhaps no question in the 
realm of agricultural chemistry or 
plant physiology has received so much 
attention as the relation of the plant 
to the nitrogen of the atmosphere and 
many points still remain to be in- 
vestigated. The question heading 
this section can best be answered by 
a very brief historical review of the 
subject. At one time it was generally 
believed that the air was the sole 
source of the nitrogen supply for the 
plant. The first important experi- 
ments that indicated the contrary 
were those of Boussingault, in which 
he grew plants in sterile soil free 
from nitrogen, the plants being so 
protected that they came in contact 
with no nitrogen save that of the air. 
The plants grew for a short time only, 
and on analysis showed that they 
contained no more nitrogen than was 
present in the seed. Similar experi- 
ments conducted by Ville gave con- 
trary results. To decide the matter a 
great number of painstaking experi- 
ments were carried out at Rotham- 
sted, England, all of which confirmed 
the results obtained by Boussingault 
and the question was considered set- 
tled by most experimenters. It oc- 
curred to an American investigator 
(Atwater) that plants grown under 
natural conditions might use free ni- 
trogen, even though they did not un- 
der the conditions of these experi- 
ments. He, therefore, grew plants in 
pots in the open, analyzing the soil 
before, and the soil plus the plant at 
the end of the experiment, correcting 
for the nitrogen carried down in the 
rain water. He found that while in 
most cases there was no gain of nitro- 
gen, in some cases there was and that 
the plants showing a gain of nitrogen 



invariably belonged to the legumes. 
It remained for Hellrlegel to explain 
this phenomenon. He repeated the 
experiments of Boussingault with 
this variation, that he added to the 
soil a small quantity of water leached 
from a natural soil, so as to introduce 
any bacteria that might exist natur- 
ally in the earth. He found that the 
legumes grew vigorously while the 
cereals produced only feeble and 
short-lived plants. An examination of 
these legumes showed that they all 
had little nodules on their roots and 
these nodules were found to contain 
innumerable bacteria. 

Further experiments have demon- 
strated that when leguminous plants 
are grown in soils containing the 
proper bacteria they can indirectly 
make use of free nitrogen and are 
practically independent of the nitro- 
gen in the soil. This property is not 
a function of the legume itself, but of 
the bacteria that produce the nodules, 
and in the absence of these organisms 
the legumes are quite as dependent 
upon the supply of nitrates as are the 
other orders of plants. For all prac- 
tical purposes then, it may be consid- 
ered that clover, peas, beans, alfalfa 
and other legumes derive the bulk of 
their nitrogen from the air and that 
in growing them the farmer is not de- 
creasing the nitrogen content of the 
soil. 

(17) Inoculation of the Soil.— Ex- 
perience has shown that all soils do 
not contain the bacteria necessary to 
the fixation of free nitrogen by le- 
gumes. They may be introduced into 
a field by sowing with the seed a 
small quantity of soil from a field in 
which the legume has been success- 
fully grown. This has been done so 
often as to leave no doubt of its prac- 
ticability. Late investigations have 
shown that the same species of bac- 
teria will not do for all legumes, so that 
a soil, for instance, may grow clover 
to perfection when soy beans or al- 
falfa will not thrive on it at all. This 
fact explains many of the disappoint- 
ments experienced by farmers in the 
trials of some of the more recently 
introduced leguminous crops. 

(18) Other Ways in Which Nitrogen 
Is Fixed. — Within the last few years 
a number of bacteria have been dis- 
covered in the soil that have the 
power of using free nitrogen and 



which do not grow in connection with 
the higher plants. These bacteria are 
found in most soils and may be an 
important factor in maintaining the 
supply of nitrogen in the soil. At the 
present time it is impossible to say 
if the nitrogen added to the soil in 
this way is of any considerable mo- 
ment. 

(19) Mineral Constituents of the 
Plant. — There is still to be considered 
the mineral matter found in the ash 
(see Section 5), or that material 
which remains when the organic part 
of the plant is destroyed by burning, 
and which corresponds exactly to the 
ashes left in the stove after burning 
wood. The substances found in the 
ash are all derived fi-om the soil. It 
has not always been thought that they 
were necessary to plant growth. The 
earlier writers on agriculture consid- 
ered only the organic matter of the 
soil and certain constituents of the 
atmosphere as of any importance to 
the plant. These writers thought the 
presence of mineral matter merely 
accidental and due to the fact that the 
plant took them in because they were 
dissolved in the necessary soil water, 
and had no way of rejecting or remov- 
ing them. Later writers, pre-eminent 
among whom was Liebig, proved that 
the ash ingredients were necessary to 
the plant. A very simple experiment 
was sufficient to show that at least 
some of the mineral matter was essen- 
tial to plant growth. Seeds were 
planted in pots containing quartz-sand, 
to one of which nitrogen compounds 
alone were supplied, and to the other 
nitrogen and a small amount of plant 
ash. The plants in the pot which re- 
ceived the ash grew to maturity, while 
those in the other pot made only a 
feeble, short lived growth. 

(20) Essential and Non-Essential 
Elements. — The experiment just de- 
scribed proves that there is something 
in the ash that is required by the plant, 
but does not show whether a part only 
or all of the ingredients are essential. 
This question naturally interested a 
number of investigators and soon a 
mass of evidence was at hand. In or- 
der to determine which elements are 
essential, plants were grown, either in 
especially prepared sand, or by the 
"water-culture method," in such a way 
that they were supplied with all the 
elements occurring in plants with the 
exception of the one element under in- 



vestigation. If the plant grew to ma- 
turity the element which was missing 
was deemed non-essential. If, on the 
other hand, the plant failed to de- 
velop, that particular element was con- 
sidered to be essential. 

The numerous experiments of this 
kind which have been carried on show, 
that of thC' ash constituents, potash, 
lime, phosphoric acid, magnesia, iron 
and sulphuric acid are absolutely es- 
sential to plant growth. Toward soda, 
chlorine and silica plants seem to be 
indifferent, as they can be grown to 
maturity in the absence of these sub- 
stances. For this reason it is gener- 
ally considered> that only ten of the 
thirteen elements found in the plant 
are essential to its growth, soda, 
chlorine and silica being thought non- 
essential. Accepting this view, and 
referring again to the table in Section 
5, it will be seen that 1,000 pounds 
of corn plant contain only 9 pounds of 
essential mineral matter, or about 0.9 
per cent. Attention is called to the 
fact that these experiments extended 
over only one generation and that it 
is possible that an attempt to grow 
the crop through successive genera- 
tions in a soil devoid of soda, chlorine, 
or silica might show different results. 

(21) One Element Cannot be Sub- 
stituted for Another. — The experi- 
ments mentioned above have shown, 
not only that certain chemical ele- 
ments are necessary to plant growth, 
but also that it is not possible to re- 
place these essential elements even 
by others which are similar in chem- 
ical properties. In the chemical lab- 
oratory, for instance, it is found that 
soda and potash are very much alike 
in their action, and one may be used 
in place of the other in many opera- 
tions. It would be a great thing for 
agriculture, if soda could be substi- 
tuted for potash as a plant food, as 
compounds of sodium are very cheap 
compared with potash compounds. 
This point has been thoroughly inves- 
tigated, and it has been demonstrated 
(by the latest experiments especially) 
that soda cannot take the place of pot- 
ash a,s a fertilizer. As a certain 
amount of each of these elements is 
required for a certain yield, and none 
of the elements can be replaced by an- 
other, it seems to follow that the crop 
will be limited by the amount of the 
essential elem.ent present in least pro- 
portion, compared with the require- 



ments of the crop. In other words, if 
a field of corn can olitaiu potrssh sufli- 
cient for only half a.n average crop, 
no more than tliis can be produced, no 
matter how much of the other forms 
of plant food are present. 

(22) How the Mineral Matter Enters 
the Plant. — It seems evident that the 
mineral matter must be taken up in 
some way by the roots. All are fa- 
miliar with the fact that the soil is 
not a solid mass, but consists of small 
particles or "grains" with air spaces 
between, these spaces in the surface 
foot amounting to fully half the bulk 
of the soil. These soil grains vary 
in size according to the character of 
the soil, being very fine in clay and 
comparatively coarse in sandy soils. 
The roots of the plant push down be- 
tween these soil grains, branching 
more or less, and spreading througii- 
out the soil. Surrounding the growing 
tip of the root are great numbers of 
fine root-hairs that work their way in 
between and around the small soil 
grains, adhering closely to them and 
covering an immense amount of sur- 
face. It is on these root hairs that 
the plant is dependent for the absorp- 
tion of its water and mineral food. It 
was once thought that plants actually 
took in the very small solid particles 
of soil, and that the purpose of culti- 
vation was to render the particles 
small enough for the plant to absorb 
It is now known that no food can enter 
the plant unless it is in solution. Each 
soil grain is surrounded by a film of 
water, and this water contains dis- 
solved in it small quantities of the 
mineral ingredients of the soil, includ- 
ing nitrogen in the form of nitrates. 
The root hairs absorb the moisture as 
it is I'equired by the plant and with it 
such mineral matter as it needs. Both 
water and the dissolved matter enter 
the plant by the process known as 
osmosis, a process tliat cannot be ex- 
plained in the brief space allotted to 
this subject. Suffice it to say. that 
each element is absorbed indepen- 
dently of the others, and that the 
plant can, in a way, refuse to absorb 
more of any one ingredient, when it 
has all that is needed for its growth. 
This "selective power" of the plant 
(if it may be so called) is shown by 
the fact that two different kinds of 
crops grown on the same soil may dif- 
fer greatly in their composition. The 
ratio betvi^en the chemical elements 
found in them may be entirely differ- 



ent in the two crops and may be, in a 
great measure, independent of the 
ratio existing between these elements 
in the soil water. 

(23) Soil Solutions Very Dilute.— 

The amount of mineral matter dis- 
solved in the soil water is very minute. 
In Section 6 attention was called to 
the fact that at least 300 pounds of 
water must pass through the plant to 
produce one pound of dry matter. The 
fact that the soil water contains mere 
traces of plant food probably accounts, 
in some measure, for the immense 
quantity of water used by the plant, 
as it must absorb this water to obtain 
the food it requires. The plant is not 
entirely dependent upon the mineral 
matter actually dissolved in the soil 
water for its supply of food. The roots 
have the power of secreting an acid 
substance that has a solvent action on 
that part of the soil that is insoluble 
in pure water. This is shown by the 
root tracings often seen on pieces of 
limestone in the soil. It may be shown 
by growing a plant in a small quantity 
of soil placed on a piece of marble. If 
the marble is examined after a time, 
the outlines of the roots can be seen 
distinctly where the acid substance 
has cut into its surface. How great a 
factor this property of the plant is, 
cannot be stated at present. 

(24) Function of the Different Food 
Elements. — Now that the source of the 
different elements required by the 
plant has been briefly discussed, some 
of the readers of this article may de- 
sire to have explained the special func- 
tion in the vital processes of the plant, 
that is performed by each of these sub- 
stances. Unfortunately but little is 
known in regard to this subject, for 
up to the present time it has almost 
defied investigation. Carbon, oxygen 
and hydrogen are found in all the or- 
ganic compounds of the plant, and, as 
has been shown, form 98% per cent 
of the green corn crop. Nitrogen is 
a constituent of proteids and is neces- 
sary to their formation. Sulphur is 
found in some of the proteids, but its 
special function is not known. Phos- 
phoric acid is supposed to be in some 
way connected with the transportation 
of the proteids from one part of the 
plant to another. Potash is thought 
to be necessary to the conversion of 
starch into sugar, and, consequently, 
its removal from the leaves to other 
parts of the plant. As starch itself 



is insoluble, it must be converted into 
sugar before it can be transported. 
Iron is necessary to the production of 
chlorophyll. A plant grown in a soil 
devoid of iron contains no chlorophyll 
and, therefore, does not possess the 
power of fixing carbonic acid gas and 
manufacturing starch. Lime probably 
performs a number of functions, one 
of which is to neutralize the poisonous 
oxalic acid formed in the plant and 
render it harmless by producing the 
insoluble calcium oxalate. Of the part 
played by the other elements practi- 
cally nothing is known. 

(25) Other Ways in Which Plant 
Food Is Lost. — In Section 3 it was sug- 
gested that the decrease in fertility of 
a soil might be due to the fact that 
the crop removes from it something 
that is essential to plant growth, and 
the following sections have been de- 
voted to determining what these essen- 
tial elements are. Before proceeding 
to apply the knowledge thus gained, it 
is desirable to mention briefly two or 
three ways in which plant food may be 
lost other than by removal of the crop. 
First, by leaching of the soil, or re- 
moval of plant food in the drainage 
water. For practical purposes, nitro- 
gen may be said to be the only ele- 
ment lost in this way. As the nitro- 
gen removed by leaching is all in the 
form of nitrates, any loss from this 
cause is extremely unfortunate. The 
soil has the power of fixing most of 
the mineral elements so that only 
traces of them are lost in the drain- 
age water. The fact that certain min- 
eral fertilizers are fixed by the soil 
can be shown by a simple experiment. 
A tall cylinder is filled with soil and 
to it is added a quantity of water in 
which is dissolved compounds con- 
taining nitrate nitrogen, phosphoric 
acid and potash. If the water that 
leaches through this soil is analyzed 
it is found that the potash and phos- 
phoric acid have been removed by the 
soil, but that the nitrogen all remains 
in the leachings. 

Second, by surface washing. In 
hilly countries this may be a very im- 
portant factor. As the soil is removed 
bodily from the surface of the field, 
it follows that the loss in this case 
falls on all the food elements. It 
affects nitrogen and phosphoric acid 
more than the other ingredients. Most 
of the nitrogen is in the organic mat- 
ter which is near the surface and, be- 



ing lighter than the rest of the soil, 
is more easily washed away. In most 
soils the first foot contains a larger 
proportion of phosphoric acid than the 
subsoil. 

Third, by denitrification. This has 
been referred to in Section 15 and may 
be of great moment in a soil that is 
not properly managed. The conditions 
that are desirable in the soil are such 
as best prevent denitrification, so that 
the farmer who understands his busi- 
nes need not fear this source of loss. 

It will be seen that in all these cases 
the heaviest loss falls on the nitrogen, 
the most expensive element to sup- 
ply, and emphasizes a former state- 
ment, that the maintenance of fertility 
is largely a question of an adequate 
supply of nitrogen. 

The next subject to be discussed is 
the amount of plant food removed by 
the crop in its relation to the com- 
position of the soil. 

(26) A Small Part of the Plant 
Food Is Derived From the Soil. — At- 
tention is again called to the fact that 
the atmosphere is the original source 
of 98% per cent, of the materials 
found in the green plant; the carbo- 
hydrates, fats and fiber being com- 
posed of elements supplied in the 
form of water and carbonic acid gas. 
These substances are furnished free 
of cost in humid climates, the supply 
being practically beyond control, and 
their use by the plant results in no 
impoverishment of the soil. The sub- 
ject of practical importance to the 
farmer is the supply of the other lYz 
per cent, of the plant, consisting of 
nitrogen and the ash elements which 
are derived directly from the solid 
portions of the soil. It has been 
shown that seven of these elements 
are essential to plant growth. Ex- 
perience has proven that only three 
of these elements (i. e., nitrogen, 
phosphoric acid and potash) are likely 
to become exhausted, or in other 
words, that nothing is gained by add- 
ing to the soil any of the other ele- 
ments of plant food. This is due to 
the fact that the plant uses nitrogen, 
phosphoric acid and potash in rather 
larger quantities than the other ele- 
ments, and that they existed in 
smaller quantities in the soil, and not 
because they are any more essential 
to the plant. Occasionally soils are 
found that are actually deficient in 
lime, but in most cases lime is pres- 



10 



ent in sufficient abundance for the 
growth of the plant. In this study 
of the effect of the removal of the 
crop upon the amount of plant food in 
the soil, then, it will simplify matters 
to confine attention to the three sub- 
stances, nitrogen, phosphoric acid and 
potash, assuming that all the other 
elements are present in the soils in 
abundance. 

(27) Amount of Fertility Removed 
by Crops. The different crops vary 
greatly in the amount of the three 
valuable fertilizing ingredients which 
they contain. The following tables 
gives the amovint of nitrogen, phos- 
phoric acid and potash in 1,000 pounds 
of some of the important crops, the 
different materials being selected to 
show something of the range of com- 
position. 

Table 2. — Amount of fertilizing in- 
gredients in crops: 



Table 3. — Amount of fertility re- 
moved from an acre: 



1000 POUNDS OF- 



Corn Fodder, with ears. 

Corn, ears only 

Timothy Hay 

Wheat, grain 

Oats, grain 

Clover Hay 

Tobacco 

Cabbage 

Potatoes 



■a o 

3.- 



3ja o 



17.6 

14.1 
12.6 
20.2 
16.5 

21.2 

24.5 

2.4 

5.7 



cq. 



8.9 

4.7 
9.9 
5.5 
4.8 
18 7 
40.9 
5.8 
3.8 



Notice the great difference in the 
amount of fertilizing materials re- 
moved in one thousand pounds of the 
various crops as shown especially in 
the table under nitrogen and potash. 
For the purpose of this discussion the 
per cent, of fertilizing ingredients in 
the crop is not of so much importance 
as the total amount removed by it 
from each acre of ground. The next 
table gives the amounts of nitrogen, 
phosphoric acid and potash removed 
from an acre by a few of the com- 
mon crops. (Compiled by Van 
Slyke.) 



KIND OF CROP 



Corn, grain only. 

Clover Hay 

Cabbage 

Barley 

Wheat 

Wheat 

Oats 

Tobacco 

Timothy Hay. . . 





s 




YIELD 


M- a 

o V 

.£2 




45 bus. 


63 


24 


2 tns. 


82 


18 


15 *' 


100 


35 


30 bus. 


56 


17 


15 " 


31 


10 


30 " 


62 


20 


45 " 


45 


16 


1600 lbs. 


76 


16 


1)4 tns. 


38 


15 



o 

3" 



26 

88 
135 
51 
13 
26 
37 
200 
45 



An interesting point brought out by 
the table is the great difference in 
the total amount of plant food re- 
moved from an acre by the various 
crops. It is readily seen that certain 
crops must exhaust the fertility of 
the soil more rapidly than others, and 
common experience shows that the 
plants which remove large quantities 
of the essential plant foods are those 
that most quickly render the soil un- 
fertile. 

(28) Amount of Plant Food in the 
Soil. — The bearing of the above facts 
upon the question of the maintenance 
of fertility cannot be fully shown un- 
less the amount of plant food existing 
in the soil is determined. Large num- 
bers of analyses of soils have been 
made and, as might be expected, these 
analyses show great variations in the 
composition of the soils. The follow- 
ing table gives the amount of nitro- 
gen, phosphoric acid and potash in 
the first foot of typical sandy loam, 
clay loam and clay soils. 

Table 4. Amount of plant food per 
acre in the surface foot. 



KIND OF SOIL 



Sandy Loam 
Clay Loam. . 
Clay 



a 


V 






u 


a o 


- cl 


u. <« 


P i- 


O ,u 


11 a, 


J3 TS 1) 


o . 


g- u a 


t <« 


0< oi 


•-.D 


ja ,D 


;2;i-i 


0, p 


3,736 


7,326 


4,789 


4,935 


3,250 


5,600 



28,669 
44,827 
12,600 



The large amount of plant food 
present in the soil is surprising in 



11 



view of the fact that it is so hard to 
maintain a satisfactory j'ield of crops. 
Comparing tables three and four it 
is seen that the analyses of the clay 
loam soil shows the presence of suffi- 
cient nitrogen for 77 crops of wheat 
yielding 30 bushels to the acre; 
enough phosphoric acid for 246; and 
potash to supply 1724 such crops. The 
second and third foot contain nearly 
as much phosphoric acid and potash 
as the surface foot, so that so far as 
these two substances are concerned 
the supply seems almost inexhausti- 
ble. Although the chemical analyses 
of many soils upon which wheat has 
been grown show fully as large 
amounts of plant food as the clay 
loam under discussion, experience has 
demonstrated that long before the 
smallest number of crops mentioned 
above (i. e., 77,) have been produced 
the yield has so decreased as to be 
unprofitable. 

(29) Chemical Analysis Does Not 
Show Available Plant Food. — The 
reason for the apparent inconsistency 
between the analyses of soils and the 
actual results in raising crops is 
found in the fact that the chemical 
analyses give the total amount of 
nitrogen, phosphoric acid and potash 
in the soil, but do not indicate what 
part of these foods is available to 
the plant. The greater proportion of 
these substances is locked up in in- 
soluble compounds in which form the 
plant is incapable of using them. 
Smaller quantities have been changed 
by the forces of nature into forms in 
which they are available to plants. 
While the amounts of these materials 
removed by the crop seem insignifi- 
cant when compared with the total 
plant food in the soil, they may be 
very large in comparison with the 
available part. The unavailable or 
"potential" plant food, is gradually 
being made available, but not with 
sufficient rapidity to replace that re- 
moved from the field at harvest. It 
will thus be seen that present fertility 
of the soil depends not upon the po- 
tential plant food it contains, but 
upon that which is immediately avail- 
able to the plant, and the yield will 
be limited by the element of this 
available plant food present in least 
quantity. Continual cropping of the 
soil, with the removal of everything 
from the field, results in the exhaus- 
tion of the plant food that has been 



rendered available during the past 
ages. The next subject that suggests 
itself is the origin of the plant food 
and the manner in which it became 
available to plants. 

(30) Origin of the Soil. — All soils 
are derived primarily from the igne- 
ous or original rocks, of which the 
granites, trap, etc., are good exam- 
ples. Geology teaches that the earth 
was once a molten mass, and that, 
on cooling, it solidified into rocks, of 
which those mentioned are types. 
These rocks must have contained all 
of the mineral or ash elements of 
plant food, as no other source of 
them is conceivable. This plant food, 
however, was present in insoluble 
compounds and in this form was not 
available to plants. The conversion 
of this potential plant food into avail- 
able forms was brought about by a 
number of agencies. Fortunately 
these changes can be studied at first 
hand in the lava beds resulting from 
volcanic eruptions, and which have 
been transformed, in an incredibly 
short time, from beds of solid rock 
into more or less fertile soils, by a 
series of changes much like those to 
be described. 

Evidently the first step toward the 
conversion of the solid rock into soil 
must have been the act of pulveriza- 
tion. A number of natural agencies 
have taken part in the grinding of the 
original rock into the small particles 
in which they are found in the soil. 
The rocks have been disintegrated 
through the influence of heat and 
cold, freezing and thawing, and by 
the action of air, water and ice. Such 
rocks as the granites, for instance, 
can easily be seen to consist of sev- 
eral different minerals. These sub- 
stances are differently affected by 
heat and cold, expanding and contract- 
ing at different rates, and for this 
reason the effect of changes in tem- 
perature is to separate the rock into 
its component parts. All rocks are 
more or less porous and consequently 
absorb water, and the expansion of 
this water upon freezing tends to 
break the mas sinto fragments. Per- 
haps more important in this grinding 
process than either of these factors 
is the action of running water, and 
moving ice in the form of glaciers. 
There is not space to discuss these 
forces in detail, but it will be suffi- 
cient for the purposes of this paper 



12 



if it is kept in mind tliat all these in- 
fluences combine to disintegrate and 
grind the surface rocks into smaller 
and smaller fragments, until they are 
reduced to the finest particles found 
in what is called the soil. 

A soil produced by mere pulveriza- 
tion of the rocks would not furnish 
proper food for the higher plants, as 
one can readily imagine if he thinks 
how unsuitable pulverized granite 
would be for plant production. The 
essential elements locked up in these 
insoluble compounds must be trans- 
formed into materials that the plant 
can assimilate, and water is an im- 
portant factor in bringing about these 
chemical changes. Pure water has 
very little solvent effect upon the min- 
erals of which the igneous rocks are 
composed. The water that enters the 
ground has dissolved in it small 
amounts of carbonic acid gas derived 
from the air and water containing this 
gas will dissolve these minerals in 
appreciable quantities. 

All the processes enumerated unite 
in transforming the mineral matter 
of the rocks into forms available to 
plants, but the mineral foods alone 
cannot support the higher plant life. 
It has been sliown that to grow crops 
the soil must contain ava.ilable nitro- 
gen, and this must have originally 
been derived from the air. In a pre- 
vious section (13) it was mentioned 
that small quantities of combined ni- 
trogen were carried into the soil by 
the rain-water and this amount, 
though very small, would probably be 
sufficient to enable plant growth to 
begin. Some bacteriologists believe 
that the species of bacteria mentioned 
in section (18), which can live on min- 
eral food alone, deriving all their ni- 
trogen from the air, were important 
factors in the early nitrogen supply 
of the soil. 

Vegetation begins with the very 
simplest forms of plants and is of 
course very scanty at first. These 
plants on dying become a part of the 
soil, all of the plant food used by them 
being thus returned. Food that has 
once been used by plants is very read- 
ily made available to succeeding 
crops, through the processes of decay 
and nitrifxCation Vfhich have been de- 
scribed. The soil is now able to pro- 
duce a larger crop, as it contains the 
plant food in the previous growth in 
addition to that added through the 



agencies detailed above. In this way 
the growth gradually becomes more 
abundant. The plants on decaying 
give rise to humus and this increases 
the fertility of the soil both by being 
a source of plant food and by increas- 
ing its water-retaining power. It will 
be shown later that humus is a very 
important factor in fertility. During 
the decomposition of the plants that 
give rise to humus, acid substances 
are formed which act on the rocks in 
such a way as to make more of the 
plant food available. One of the pro- 
ducts of decay or fermentation is car- 
bonic acid gas and this is dissolved in 
the soil-water and, as has been men- 
tioned, water containing this gas is 
an important help in disintegrating 
the rocks. 

As the plant food increases from 
these various causes the lower and 
simpler forms of plant life are gradu- 
ally replaced by those which are more 
highly organized. With the advent 
of plants bearing roots other factors 
in the formation of soils are intro- 
duced. The roots secrete an acid sub- 
stance that has a solvent effect on the 
mineral matter of the soil (see sec- 
tion 23), and assist mechanically in 
breaking down the rocks. All are fa- 
miliar with the tremendous force ex- 
erted by plants in breaking apart 
rocks and stone if once their tender 
rootlets obtain a foothold in a crevice. 
The roots penetrate the soil some- 
times to great depths and, as they de- 
cay after the death of the plant, they 
leave little channels in the soil which 
serve to carry down water laden with 
carbonic acid, as well as to introduce 
the oxygen of the air that, in its turn, 
is a factor in bringing about chemical 
changes in the soil which assist in 
making plant food available. 

Sooner or later in the process of 
soil formation, plants of the pulse 
family (leguminous plants) such as 
clover, vetches lupines, etc., become 
introduced. These plants, as has been 
shown, can, through the agency of 
the nodule forming bacteria in the 
soil, derive part of the food from the 
free nitrogen of the atmosphere. This 
peculiar property of leguminous 
plants is of paramount importance, 
for it is undoubtedly Nature's prin- 
cipal method of increasing the supply 
of nitrogenous food in the soil (see 
section 16). The nitrogen compounds 
accumulated by tliese plants eventu- 



13 



ally become a part of the soil through 
their decay. 

(31) Nature's Methods Contrasted 
With Man's. — The important lesson to 
be learned from a study of the origin 
of the soil is, that nature undisturbed 
has many ways of adding to the sup- 
ply of available plant food. The va- 
rious forces that have been under 
discussion have all tended to change 
more and more of the potential food 
into forms that can be assimilated by 
the plants sO' that the amount of vege- 
tation which the soil can produce has 
been constantly increasing. Under 
natural conditions, this growth is not 
removed from the ground but is again 
made available, so that the soil is 
constantly increasing in fertility. It 
will thus be seen that the fertility 
of the virgin soils is the result of ac- 
cumulations due to a variety of forces 
acting doubtless through countless 
ages, a period during which practi- 
cally nothing had been removed from 
the soil while much had been added 
to it. 

Man, on the other hand, has re- 
versed this process, and while adding 
little to the soil has removed much 
from it. Through the constant har- 
vesting of crops and by leaving the 
ground bare and exposed to the action 



of the elements, he is rapidly deplet- 
ing nature's store of food and the 
yield steadily becomes smaller. The 
effect on the mechanical condition of 
the soil due to the removal of all veg- 
etation is serious, for in this way the 
soil is deprived of its humus making 
materials which is unquestionably 
quite as important as the actual loss 
of the chemical elements of fertility. 

(33) How to Prevent Exhaustion of 
the Soil. — Although Nature's method 
of maintaining the fertility of the soil 
is without doubt the most effective, 
it is of course impracticable for the 
farmer, for he must remove most of 
his crops from the field in order that 
they may be put to the various uses 
for which he raises them. A study of 
the formation of the soil, however, 
suggests two things that he can do 
to prevent the exhaustion of the fer- 
tility. The first is to so treat the soil 
as to assist and hasten nature in the 
process of converting potential plant 
food into available forms; and to 
guard against a too complete destruc- 
tion of the organic matter in the soil. 
The second is to return to^ the soil 
an amount of nitrogen, phosphoric 
acid and potash equivalent to that re- 
moved by the crop. 



PART II. Making Potential Plant Food Available. 



(34) Tillage. — The most efficient 
means of assisting nature in the con- 
version of unavailable food into forms 
that the plant can use is good tillage 
of the soil. Tillage, in the sense in 
which it is used in this article, signi- 
fies any operation of stirring and pul- 
verizing the soil by means of plows, 
harrows, cultivators or any other im- 
plement, either before or after the 
seed is sown. Obviously it would not 
be in keeping with the purpose of this 
paper to describe the tools to be used 
or the methods of operation, so that 
a brief account of the benefits to be 
derived from tillage is all that will 
be considered here. 

The most noticeable result of thor- 
ough tillage is that the soil is made 
finer, the large lumps being broken up 
into smaller particles, and in this way 
nature's work in the formation of soils 
is accelerated. Pulverization of the 
earth is beneficial in many ways. In 
the first place, loosening the soil 
makes it easier for the plant roots 



and root-hairs to penetrate it. It has 
been mentioned (22) that all soils are 
composed of grains, of greater or 
smaller dimensions, separated by air 
spaces. The tender root-hairs must 
push their way in between these soil- 
grains as it is impossible for them to 
penetrate the solid particles them- 
selves. It must be evident that the 
more the soil is pulverized the larger 
the number of the openings between 
grains, and, consequently, the greater 
the room for root growth. 

The plant is dependent upon the 
root-hairs for its supply of mineral 
food, and as these hairs grow only be- 
tween and around the soil grains, it 
is apparent that they can feed only 
on the surfaces of these particles. 
Good tillage increases the amount of 
surface exposed to the roots by break- 
ing the large lumps into small grains; 
the more complete the pulverization 
the larger the area from which the 
plant can obtain its food. The rapid 
increase of surface due to breaking 



14 



down the lumps in a soil in poor tilth 
seems almost unbelievable to one who 
has given the subject no thought. An 
example will serve to illustrate what 
is meant: A cube two inches on the 
side presents a surface of 24 square 
inches. If this cube is cut once in 
each direction, eight cubes are formed, 
each one inch on a side, giving a total 
of 48 square inches of surface, so that 
cutting only once in each direction 
doubles the amount of surface, and, 
theoretically, a plant should be able 
to derive twice as much food from the 
eight small cubes as from the large 
one. 

Tillage not only increases the 
amount of surface on which the plants 
can feed, but, at the same time, en- 
larges the water supply of the plant 
by giving the soil greater capacity for 
holding moisture. Attention has been 
called to the fact that each soil-grain 
is surrounded by a film of water which 
isi called the capillary water or film 
moisture. The plant is dependent on 
this film moisture for its supply, and 
it is readily seen that the amount of 
capillary water that the soil can hold 
depends upon the aggregate surface 
area presented by the particles of 
which it is composed. The rate at 
which this area and the consequent 
amount of available moisture increases 
is strikingly brought out by King, in 
his book entitled, "The Soil," from 
which the following is quoted: "Sup- 
pose we take a marble exactly one 
inch in diameter. It will just slip 
inside a cube one inch on a side, and 
will hold a film of water 3.1416 square 
inches in area. But reduce the diam- 
eters of the marbles to one-tenth of an 
inch, and at least 1,000 of them will 
be required to fill the cubic inch, and 
their aggregate surface will be 31.416 
square inches. If, however, the diam- 
eters of these spheres be reduced to 
one-hundredth of an inch, 1,000,000 of 
them will be required to make a cubic 
inch and their total surface area will 
be 314.16 square inches. Suppose, 
again, the soil particles to have a 
diameter of one-thousandth of an inch. 
It will then require 1,000,000,000 of 
them to completely fill the cubic inch, 
while their aggregate surface must in- 
crease to 3141.59 square inches." An- 
other way of stating the same fact is 
that if an acre of ground is so tilled 
as to reduce the average diameter of 
the soil particles to one-tenth the orig- 
inal diameter, the plant now has ten 
acres from which to draw its supply 



of water and mineral food for each 
acre it had before; and the soil is en- 
abled to hold as film moisture ten 
times as much water as it could in 
the first instance. It must be appar- 
ent that the loosening of the ground 
incident to tillage wakes it easier for 
the rainwater to enter the soil and 
tends also to prevent loss by surface 
washing. 

Tillage is useful in the spring in 
causing the soil to dry out more quick- 
ly so that planting may be done, and 
also has a tendency to make the 
ground warmer. For this purpose it 
is conducted in such a way as to ex- 
pose the maximum amount of surface 
to the action of the sun and atmos- 
phere. I.iater in the season tillage is 
used to prevent loss of moisture, and 
for this purpose the process is so car- 
ried on that a thin layer of very dry 
earth is produced at the surface to 
prevent evaporation. Under ordinary 
conditions, where the soil is some- 
what firm, water is drawn up from 
below by capillary attraction to re- 
place that removed from the surface 
by evaporation. As this evaporation 
may be very rapid in the hot, dry 
weather of midsummer, the result is 
that the water is virtually pumped out 
of the soil until it is too dry for good 
plant growth. If something is done 
to break this capillarity, the water 
cannot be brought up from below. 
This is the end accomplished by the 
"earth mulch" which is simply a layer 
two or three inches deep of very dry 
soil, so dry and loose that it cannot 
take up the water from the layer next 
beneath it. The same end can be at- 
tained by covering the ground with 
loose straw or other similar material, 
the principle underlying both kinds of 
treatment being the same. To make 
an effective earth mulch the cultiva- 
tion should be shallow and frequent; 
the aim being to make the layer as 
dry as possible. A rain, of course, will 
again compact the loose earth and re- 
new the capillarity, so that the culti- 
vation should be repeated as soon as 
possible after a rain. Even in absence 
of rain the mulch will sooner or later 
become compact of itself if left too 
long without stirring. Thorough cul- 
tivation of the soil tends to keep the 
temperature as well as the water sup- 
ply more uniform. 

Stirring the soil is beneficial in 
bringing together particles which have 
not before come into contact. In this 



15 



way chemical changesi may take place 
that render potential plant food avail- 
able, for substances having different 
chemical properties are thus enabled 
to act upon each other. The changes 
whereby potash and phosphoric acid 
become "fixed" in the soil are reac- 
tions of this class. (25). 

The changes brought about by freez- 
ing and thawing may also be acceler- 
ated by proper tillage. This is made 
use of by some farmers who plow 
heavy, lumpy land in the fall so that 
it may be exposed to the influence of 
the weather during the winter. For 
this purpose the land is so plowed as 
to leave it rough and with the largest 
possible area exposed to the weather. 
Freezing and thawing bring about dis- 
integration of the clods in much the 
manner mentioned in the section on 
formation of the soil, and the result- 
ing improvement is most remarkable 
in some classes of soils. 

One of the most beneficial results to 
be obtained from tillage is the aeration 
of the soil. The introduction of the 
oxygen of the air into the soil is of 
benefit in a number of ways. In the 
first place a certain amount of air in 
the soil is necessary for the growth 
of all plants usually raised on the 
farm. The roots cannot live without 
air any more than those parts which 
grow above ground. That air is need- 
ed by the roots can easily be shown 
by placing a pot containing any ordi- 
nary plant (not an equatic plant) in 
a jar of water so that the soil will 
always be saturated. In a short time 
the bad effects will be noticeable on 
the plant. The plant does not decline 
because the water is injurious but 
because the presence of the water ex- 
cludes the air from the roots. 

The oxygen of the air has a direct 
chemical action on the mineral matter 
of the soil that tends to make it solu- 
ble. It also prevents the formation of 
certain compounds (notably the sul- 
phides of iron) which are injurious to 
vegetation. 

AH fertile soils contain a considera- 
ble amount of organic matter and the 
presence of oxygen is necessary to its 
decomposition. Attention has been 
called to the fact that the soil con- 
tains innumerable bacteria, a part, at 
least, of which are concerned in the 
decay of the organic matter, and 
those which are beneficial to the 
farmer cannot live without oxygen. 
One class of these bacteria decompose 



a part of the organic matter with the 
formation of carbonic acid gas, and it 
has been shown that this gas dissolved 
in the soil water is a great factor in 
making plant food soluble. As this 
decomposition goes on more rapidly in 
well-aerated soils it will be seen that 
this is one reason for the increased 
fertility due to thorough tillage. The 
nitrifying bacteria previously men- 
tioned (14) thrive only in the pres- 
ence of a sufficient supply of oxygen. 
It has been shown that most of the 
nitrogen of the soil is locked up in 
insoluble organic compourids and that 
before it can be used by plants it 
must be converted into the form of 
nitrates. This process only takes 
place in a soil well supplied with oxy- 
gen, and experience has proven that 
this process is very materially hast- 
ened by frequent cultivation. The ex- 
treme importance of this process of 
nitrification has already been com- 
mented upon (14). and it only remains 
to say that tillage would pay for itself 
if it did no more than hasten nitrifica- 
tion. 

The bacteria that enable leguminous 
plants to use free nitrogen are also 
dependent on the air in the soil, for 
not only do they need oxygen, but ex- 
periments have shown that it is only 
from the air in the soil that they can 
draw their supply of nitrogen. It is 
necessary, therefore, in order that le- 
guminous plants may profit by the 
nodule forming bacteria, to have the 
soil in such a condition of tilth that 
the air may freely circulate through it. 

Thorough aeration of the soil also 
prevents the action of the denitrifying 
bacteria (15), as these bacteria thrive 
best in a soil devoid of oxygen. Acid- 
ity of the soil is also favorable to the 
growth of the denitrifying bacteria, 
and the presence of sufficient oxygen 
in the soil tends to keep it sweet (i. e., 
to prevent the formation of acid). 

Lastly, tillage is useful in destroy- 
ing weeds. It is undesirable to allow 
weeds to grow because they rob the 
crop of its moisture and plant food. 
All plants during their growth pump 
up water by means of their roots and 
give it off through the leaves. It has 
been shown (6) that at the best the 
supply of water in the ground is sel- 
dom sufficient for a maximum crop, 
so that any water that is drawn from 
the soil by the weeds works a positive 
injury to the desirable plants. While 
it is probable that the weeds work 



16 



greatest injury to the crop by depriv- 
ing it of water they also rob it of its 
mineral food. Some farmers argue 
that if the plants remain on the ground 
they are removing no plant food, but 
it must be remembered that they are 
using that portion of the plant food 
that would be available to the crop 
and that the weeds must decay before 
this food is again rendered available, 
so that so far as the present crop is 
concerned the food is as completely 
removed as it would be if taken from 
the field. 

The destruction of weeds was for- 
merly regarded as the only reason for 
tillage after seeding. It is now known 
that stirring the soil has a distinct 
value in itself and that the destruc- 
tion of weeds is really secondary. In 
fact, if the farmer so tills his soil as 
to reap the maximum benefits to be 
derived from this process he will have 
no need to worry about the weeds. 

(35) Drainage. An important meth- 
od for increasing the fertility of some 
classes of soils is that of underdrain- 
ing by use of tile or other means. Wa- 
ter exists in the soil in two principal 
conditions, viz: as the film or capillary 
moisture previously discussed (34), 
and in the form known indiscriminate- 
ly as free water, ground water, or hy- 
drostatic water. In the latter condi- 
tion the water occupies the spaces be- 
tween the soil grains, and is not held 
by the attraction of these particles. 
The surface level of this free water is 
known as the "water table" and is sit- 
uated in some soils very near the sur- 
face, while in others it is many feet 
below. The exact position of the water 
table can be readily ascertained by 
sinking a hole to such a depth that 
water will stand in it; the level of the 
water in the hole being practically 
that of the water table. It is this free 
or ground water that supplies shallow 
wells and the ordinary springs. In 
some cases the water table may be at 
or above the level of the ground, as 
is obviously the case where marshes 
and lakes exist. 

When the level of the free water is 
near the surface of the ground, the 
soil will be greatly benefited by some 
system of underdrainage as this hy- 
drostatic water is, for several reasons, 
injurious to the crop. Ground water 
limits the feeding space available to 
the plant, and, consequently, the 
amount of food it can obtain. Those 



plants that are of importance to agri- 
culture must have their roots supplied 
with air (34), and investigations have 
shown that such plants do not send 
their roots below the water table, be- 
cause the spaces between the soil par- 
ticles below this level are filled with 
water, thus preventing the entrance 
of air. In other words, the depth to 
which the plant will send its roots is 
determined by the position of the wa- 
ter table. 

Free water makes the soil cold. A 
great deal more heat is necessary to 
warm water a certain number of de- 
grees than is required to raise the tem- 
perature of the same weight of the 
dry matter of the soil the same 
amount. A soil, therefore, that con- 
tains much water is harder to heat 
than one that is comparatively dry. A 
very wet soil causes plant food to be- 
come locked up in unavailable forms 
and in some cases compounds are pro- 
duced which are actually poisonous to 
the desirable plants. An excessive 
amount of water in the soil also di- 
lutes the plant food in solution and 
makes it more difficult for the plant to 
procure sufficient nourishment. 

One of the most important consid- 
erations in this connection is the fact 
that the presence of free water in the 
soil prevents nitrification and promotes 
dentrification. In a water-logged soil 
nitrates are rapidly decomposed, the 
nitrogen being given off to the air in 
the free or elemental condition; and 
for this reason not only is the nitro- 
genous food in the soil destroyed, but 
the application of nitrogen fertilizers 
to such a soil results in great waste 
of this valuable element of fertility. 

Underdraining the field results in 
lowering the water table to the level 
of the drain, the water flowing off 
through the tile instead of standing 
near the surface as stagnant water. A 
few ways in which this is of benefit 
to the soil may be indicated. The re- 
moval of the free water from the soil 
above the drain allows the entrance 
of air, and for that reason increases 
the depth to which the roots will pen- 
etrate. The entrance of air with its 
oxygen and carbonic acid, and the con- 
sequent greater depth reached by the 
roots and earthworms, are factors of 
importance in improving the texture 
of the soil. The rains will now soak 
down through the soil instead of run- 
ning off the surface, and in this way 
the nitrogen in the rainwater is added 



17 



to the soil, and surface washing is to 
a certain extent prevented. Rain in 
the spring is warmer than the ground 
and, as it percolates through the soil, 
has a beneficial effect in warming it, 
thus putting it in condition to promote 
plant growth much earlier in the sea- 
son. Evaporation of water from the 
surface of the soil tends to keep it cool 
and, as the amount of water near the 
surface is decreased by drainage, evap- 
oration is also lessened. Well-drained 
lands, therefore, maintain a higher 
temperature throughout the season 
than do those containing much free 
water. 

Paradoxical as it may seem, under- 
draining increases the amount of wa- 
ter available to the plant. The crop 
depends almost entirely on the capil- 
lary or film moisture for its supply of 
water, and as has been said, the roots 
do not enter that part of the soil con- 
taining free water. Lowering the wa- 
ter table greatly increases the total 
amount of film moisture, as all that 
part of the soil from which the free 
water has been removed is capable 
of holding capillary water. It will thus 
be seen that while the total amount 
of water in the soil is decreased by 
drainage, that which is of use to the 
plant is made much greater. 

Drainage prevents injury from 
drouth, for by means of it the plants 
are encouraged to make deeper root 
growth and, therefore, are not so eas- 
ily affected by the extreme drying of 
the surface of the ground that takes 
place in times of scanty rainfall. It 
will readily be seen that tiling drain- 
ing determines the highest point the 
water table can reach, but tkat in dry 
weather the level of the ground water 
may be much below the drain. It is 
sometimes thought, for this reason, 
that part of the water from summer 
rains, that would otherwise be ab- 
sorbed by the soil below the drain, 
may be lost through the tile. Experi- 
ence has shown, however, that the 
water does not percolate into the 
drains, as some suppose, and that it is 
only when the rainfall is suflBcient to 
raise the water table to the level of 
the drains that any water is removed 
by them. It is a matter of common ob- 
servation that, except in the case of 
quite low lands, it is only the very 
heavy summer rains that cause the 
drains to run. It will thus be seen 
that it is merely the excess of water 



which is removed by underdraining 
and not that part which is of most 
importance to the plant. Although the 
crop probably makes little direct use 
of the free water of the soil, one must 
not lose sight of the fact that this 
water may be drawn into the upper 
layers of the soil by capillarity to re- 
place that lost by evaporation, and for 
this reason the underdraining should 
not be so deep as to interfere seri- 
ously with capillary action. 

Drainage lengthens the season of 
plant growth. Soils that are well 
drained warm up earlier in the spring 
than they would otherwise, due as has 
been explained, to the decreased evap- 
oration incident to the removal of the 
hydrostatic water, and to the fact al- 
ready mentioned that dry soils heat 
more quickly than wet ones. Plants 
need a certain amount of warmth in 
the soil before they will grow so that 
anything that increases the time that 
the soil is warmed to the proper tem- 
perature lengthens the season of 
growth. Nitrification and the other 
processes by which plant food is made 
available also take place more rapidly 
in warm soils. 

Strangely enough, experience has 
shown that it is not merely low lying 
soils which are benefited by under- 
draining. In many cases heavy clay 
soils in elevated positions, especially 
if underlayed by rather impervious 
subsoils, are greatly improved in tilth 
by tiling. In such soils the percolation 
is so slow that practically the same 
effect is produced as would be ex- 
pected if the general level of the 
ground water were near the surface. 
These soils are made more mellow by 
drainage and respond more readily to 
early tillage. Clay soils are often pud- 
dled by the fine particles in the soil 
water being deposited in the spaces 
between the soil grains, thus cement- 
ing them together. The use of tile 
will often prevent this by causing the 
water to sink more rapidly through 
the soil. Tile drained fields are not 
so apt to be injured by hauling heavy 
loads over them as are those not so 
treated. 

(36) Irrigation. There are large 
areas in this country which, for lack 
of sufiicient water, produce very 
scanty vegetation, although in many 
Instances the soil is well supplied with 
the other materials essential to the 
plant. The results to be derived from 



18 



irrigation on such soils are too well 
linown to call for common here. The 
work of investigators in the so-called 
humid climate east of the Mississippi 
(notably that of King) has shown that 
even here the total rainfall is seldom 
sufficient for a maximum yield of the 
staple crops, and the precipitation is 
distributed so unevenly throughout the 
season that a comparatively small part 
of it can be used by the crop. 

Many market gardeners recognize 
the fact that some system of irrigation 
is necessary for the most profitable re- 
turns, and are in the habit of supply- 
ing water artificially to their more val- 
uable crops. Marshall P. Wilder, 
when asked tO' name the three things 
most essential to successful straw- 
berry culture, is said to have replied: 
"First, plenty of water; second, more 
water; third, still more water." 

At the present time irrigation of the 
staple farm crops is not practiced to 
any large extent in the humid parts of 
this country. King has shown that 
the yield of these crops can be greatly 
increased by supplementing the rain- 
fall with irrigation. Two examples 
will suffice: An average of two crops 
of potatoes gave an increase of 105 
bushels per acre due to irrigation. In 
1894 he reports a crop of flint corn 
yielding 14.5 tons of dry matter per 
acre on an irrigated plot while the 
same corn yielded four tons when re- 
ceiving only the natural rainfall. 

It is more than probable that the 
future will see irrigation in extensive 
use east of the Mississippi, but at the 
present time it is only in the experi- 
mental stage and it has yet to be dem- 
onstrated that it will be profitable 
with ordinary crops under practical 
conditions. It is to be hoped that ex- 
periments along this line will soon be 
made, but they should be undertaken 
only by men who have made a study 
of the subject, for in humid climates 
irrigation in untrained hands may pro- 
duce more harm than good. 

(37) Bare Fallows. — The prac- 
tice of fallowing or resting the land is 
a very old one, being mentioned in 
the twenty-fifth chapter of Leviticus, 
where the people are commanded to 
rest the land every seventh year. 
("The seventh year shall be a Sab- 
bath of rest unto the land.") It 
would be interesting to know if this 
law was introduced into the Jewish 
code from a knowledge of tho effect 



of fallowing on the soil, or if it had 
more to do with the mystical meaning 
that seems to be associated with the 
number seven in the Hejarew religion. 

A study of the history of agricul- 
ture leads one to believe that when 
the nomadic tribes first settled down 
to anything like systematic cultiva- 
tion of the soil, they grew one crop 
(probably of the wheat family) con- 
tinuously on the same field until the 
soil became so impoverished that it 
could no longer be tilled with profit. 
They then moved to other sections, 
where virgin soil was to be found, 
and repeated the process. In the 
course of time it was discovered that 
those lands which had been aban- 
doned would again produce good crops 
after a period of "rest," as it is called. 
This led to the practice of cropping 
the land one year and allowing it to 
idle the next. It was later discovered 
that if the soil was frequently stirred 
during its resting period the growth 
on the following year would be much 
more luxuriant than if the ground 
was left undisturbed. From this be- 
ginning arose the practice of summer 
or bare fallowing, as it is understood 
today. Later experimenters found 
that practically as good results could 
be obtained by the use of the so- 
called "fallow crops" in place of the 
year of rest. These are simply crops 
like Indian corn, turnips, potatoes, 
etc., which are intertilled and kept 
free from weeds during at least a part 
of their period of growth, and their 
introduction has practically done 
away with the use of the bare fallow 
in most localities. 

It is well understood that what was 
formerly called resting the land is in 
reality a method of bringing about 
ideal conditions for the transforma- 
tion of potential food into forms avail- 
able to the plant. This practice of 
fallowing the land had practically 
fallen into disuse, but is being so 
strongly advocated in some quarters 
at the present time that it seems 
proper to briefiy discuss the subject 
here. 

The chief advantages claimed for 
summer fallowing are: (1) It makes 
plant food available, thus increasing 
the succeeding crop. (2) It enables 
one to rid the land of weeds. (3) It 
destroys large numbers of injurious 
insects. It is doubtful, however, if 
under good conditions of tillage and 



19 



soil management, fallowing is ever 
necessary. It adds nothing to the 
soil, but merely presents conditions 
that are favorable to the conversion 
of potential plant food into available 
forms, and the increase in the crop 
following the fallow is seldom suffi- 
cient to recompense the farmer for 
the year of non-production. The crude 
methods of cultivation in use in 
earlier times doubtless made fallows 
necessary, but the introduction of 
modern machinery and more rational 
methods of tillage have for the most 
part removed this necessity. 

There is no doubt of the efficiency 
of fallowing as a method of making 
plant food available, especially if the 
soil is frequently stirred. The condi- 
tions brought about by this treatment 
of the soil are just those that hasten 
nitrification, for it has been shown 
that the nitrifying bacteria thrive 
best in a warm, well aerated soil. The 
result of fallowing is that during the 
hot summer months the process of ni- 
trification goes on very rapidly, and, as 
there is no growth to remove them, 
the nitrates accumulate in the soil in 
large quantities. Attention has been 
called to the fact that the nitrates are 
easily leached out of the ground if 
present in any considerable amount. 
One of the dangers of the practice of 
fallowing is that if the land is left 
bare during the heavy rains of fall 
and winter a large part of the nitrates 
formed during the summer months may 
be lost in the drainage water, a state 
of affairs that is to be avoided if pos- 
sible. At the New York (Geneva) Ex- 
periment Station experiments were 
made to determine this point. Lysi- 
meters were constructed to simulate 
natural conditions as nearly as pos- 
sible and yet allow the collection of 
the drainage water. On one of these 
lysimeters grass was allowed to 
grow, being frequently mowed as is 
done on a lawn. The soil in another 
was kept bare, no plants at all being 
allowed to grow, and the surface was 
frequently stirred. The drainage 
water from the lysimeters was all col- 
lected and the nitrogen determined. 
It was found that in the case of the 
lysimeter on which the sod was grow- 
ing practically no nitrogen was lost in 
the drainage water, while in the 
other the loss amounted to from 218 
to 357 pounds of nitrogen per acre 
each year. There is no doubt that 



these figures are in excess of the lose 
which would actually occur under 
field conditions, as the drainage in the 
lysimeters was perfect, and there were 
practically none of the effects of cap- 
illarity which would have obtained in 
the field. They show, nevertheless, 
in a marked way the danger of great 
loss of nitrogen if the summer fallow 
is followed by heavy fall rains. It was 
found that the loss was small in the 
summer months, nearly all of it oc- 
curring during the fall and winter. 
This loss of nitrogen amounts to from 
two to four times that removed by a 
crop of corn, and it will be remem- 
bered that it is the nitrogen which is 
in the form most available to plants 
that is lost by leaching. 

These experiments are also inter- 
esting in that they show how slight is 
the danger of loss of nitrogen if a 
crop is kept growing on the land. 
Numerous other experiments have 
confirmed this observation, that if the 
field is covered with a growth of 
plants practically no nitrogen is lost 
in the drainage water, not because the 
nitrates are not formed, but because 
the plants appropriate them as fast 
as they are produced. If then, the 
field which has been lying idle dur- 
ing the summer is planted to a crop 
before the fall rains begin, the loss 
of nitrogen will probably be pre- 
vented. The whole secret of prevent- 
ing the leaching of nitrogen from the 
soil is to have some crop on it during 
all the growing season. Nitrification 
takes place very slowly after the 
warm weather of summer has passed, 
so there is i-tle danger of loss of 
nitrogen through leaving the ground 
bare in the late fall, provided a crop 
has been growing on it during the 
period that was favorable to nitrifica- 
tion. For this reason there need be 
no fear of loss of nitrogen as a result 
of fall plowing. 

There are, however, two sides to the 
question of the desirability of sum- 
mer fallows. King cites experiments 
of his own which show (by determi- 
nations made April 30) that the plots 
which had been fallow the previous 
year contained 245 pounds more 
nitrate nitrogen per acre than the 
corresponding plots on which crops 
had been produced. His experiments 
further showed that the amount of 
nitrate nitrogen in the fallow plots at 
that date was actually more than it 



20 



was on Aug. 22 of the year before. 
"From this it is clear that the crops 
on fallow ground start out in the 
spring under conditions very superior 
to those on the fields which had not 
been fallow" (King). Unfortunately 
these experiments throw no light on 
the losses through drainage, and it is 
impossible to decide whether this de- 
sirable condition in the spring has not 
been brought about by too great a 
drain on the total nitrogen supply of 
the soil. 

Summer fallowing has a tendency to 
conserve the moisture of the soil, as 
one can readily imagine when he re- 
calls the rapid rate at which plants 
remove water from the ground. (6) 
The tillage incident to the fallow also 
prepares an earth mulch and prevents 
loss of water by evaporation. At the 
Wisconsin Experiment Station it was 
found that in the spring following a 
summer fallow the land which had 
been fallowed contained 203 tons more 
water per acre than did that which 
had been cropped the previous year. 
The following quotation is the closing 
paragraph of King's work, entitled 
'•The Soil": 

"In very wet climates or more espe- 
cially in those which have heavy rain- 
falls outside the growing season, so 
that excessive percolation and loss of 
plant food through drainage is large, 
summer fallowing in broad fields can- 
not be recommended. But in dry 
countries, where the loss of plant food 
through drainage channels is small, 
broad field summer fallowing may in 
some cases prove decidedly advan- 
tageous, because with the deficient 
rainfall, there may not be moisture 
enough to mature a crop and at the 
same time to develop a sufficient 
store of plant food from the native 
fertility of the soil to meet the de- 
mands of the next season. At all 
events, the arguments urged against 
fallowing in countries like England 
do not apply to tne semi-arid districts 
of the world with equal force!" 

The claim that fallowing is efficient 
in the destruction of weeds and in- 
jurious insects is a valid one, but the 
same results can probably be obtained 
by a judicious rotation and by the use 
of cultivated crops, without allowing 
the ground to lie idle. After all, the 
practical question is whether the one 
crop after the fallow is equal to the 



two crops that would otherwise be 
produced, and the concensus of opin- 
ion among practical farmers seems to 
be that it is not. This is one of the 
many problems in agriculture which 
calls for more thorough investigation 
and, fortunately, is receiving the at- 
tention of some of our experiment sta- 
tions at the present time, so that 
more scientific data may be hoped 
for in the near future. 

While the long summer fallow is to 
be recommended only when the soil 
has been abused and has become so 
foul with weeds that no other method 
will remove them, frequent use should 
be made of the short fallow (i. e., be- 
tween crops). It will be found ad- 
vantageous in many instances to plow 
the land immediately after the re- 
moval of one crop and keep it well 
stirred until the planting of the next. 
By this means loss of moisture from 
the soil is prevented and the decom- 
position of the organic matter is has- 
tened, so that a large supply of plant 
food is prepared for the succeeding 
crop. Barley or clover, for instance, 
is often followed by a fall planted 
grain and some weeks intervene be- 
tween the harvesting of the one and 
the planting of the other. If the field 
be plowed immediately after the 
first crop has been removed and cul- 
tivated frequently the results will be 
beneficial in starting the next crop 
with a larger supply of nitrates and 
moisture than would have ben pres- 
ent if the ground had remained un- 
disturbed. 

In the case of the fallow or culti- 
vated crops previously mentioned the 
process of nitrification between the 
rows is accelerated, as it is in the 
bare fallow, but the growing plants 
appropriate the nitraites almost as 
rapidly as formed and hence prevent 
loss of nitrogen in the drainage of 
water. 

(38) Humus and Green Manuring. — 

Loss of fertility in a soil is, in a great 
number of instances due to the rapid 
decrease in the amount of humus 
which it contains. Humus is the 
product formed by the partial decay 
of organic matter, and is the material 
that gives the rich, black appearance 
to some soils. It is formed in most 
cases from the plants which have 
previously grown on the field, and 



21 



have later become a part of the soil. 
It may also arise from animal or 
vegetable materials added as manures. 
Virgin soils are comparatively rich 
in humus, but investigation has 
shown that continued cropping with 
no provision for maintaining the sup- 
ply of humus may result in its be- 
ing decreased from one-third to one- 
half in a period of not more than fif- 
teen years. 

Humus is generally considered to 
be a necessary ingredient of fertile 
soils. To be sure, soils may be pre- 
pared containing no organic matter 
which will produce good crops under 
artificial conditions, where the water 
supply, etc., are under complete con- 
trol. Under field conditions, however, 
a sufficient supply of humus is of par- 
amount importance. Humus increases 
the power of the soil to absorb and 
retain water and, consequently, a crop 
grown on a soil containing a fair 
amount of humus is less likely to suf- 
fer from drouth. The following table 
giving the amount of water held in a 
cubic foot of the different varieties of 
soil illustrates this point. 

Pounds of water 
Kind of soil. in one cubic foot. 

Sand 27.3 

Sandy clay 38.8 

Loam 41.4 

Humus 50.1 

It will be seen that the quantity 
of water increases with the amount of 
humus present, the sand containing 
the least and the loam, which has the 
largest percentage of humus, with the 
exception of the strictly humus soil, 
containing much more. The organic 
matter in the high humus soils acts 
like a sponge to absorb the water, 
but at the same time holds it in such 
a condition that it is available to the 
crop. The peats are examples of ex- 
treme humus soils and, as is well 
known, may hold more water than is 
desirable. 

Humus is also valuable in improv- 
ing the physical condition of the soil. 
Sandy soils are made more compact 
by its presence and better able to 
supply the crop with moisture. Clay 
soils, on the other hand, are made 
more mellow by the addition of humus 
forming materials. Clay is liable to 
become too^ compact unless there is a 
certain amount of organic matter 

22 



present to prevent it. In other words, 
humus forms loam, for a sandy loam 
is simply a sandy soil well supplied 
with oi-ganic matter, and a clay loam 
is clay which has been made light 
and mellow by the same material. 

Humus is of importance because it 
is a store hc'ise of plant food, espe- 
cially nitrogen. It has been shown 
that most of the nitrogen of the soil 
is present in the more or less decom- 
posed organic matter. Besides the 
nitrogen the humus contains phos- 
phoric acid and potash in higaly avail- 
able forms, or assists in rendering 
them available, for the crop is en- 
abled to obtain much more of these 
substances from a soil rich in humus 
than from one in which the humus 
content is low. 

The presence of decomposing or- 
ganic matter in the soil is an import- 
ant factor in making the mineral ele- 
ments of plant fo©d available. Dur- 
ing decay certain acid substances, 
known collectively as humic acid, are 
produced, and these undoubtedly have 
a solvent action on the mineral mat- 
ters of the soil, tending to make them 
more available to the plant. Perhaps 
quite as important a factor is the 
large amount of carbonic acid formed 
during the process of decomposition. 
This carbonic acid dissolved in tho 
soil water is of prime importance in 
the production of soluble plant food, 
and it also has a beneficial effect on 
the phya "al condition of the soil, 
especially if the soil contains a large 
amount of clay. 

Humus prevents extremes of soil 
temperature. A soil containing a 
sufficient supply of organic matter 
does not respond to changes of tem- 
perature so readily as one deficient in 
humus. The latter warms up some- 
what more slowly and retains itsi 
heat for a longer period. 

Experiments conducted in Minne- 
sota and North Dakota have shown 
conclusively that as the humus con- 
tent of the soil is decreased by con- 
stant cultivation and cropping (espe- 
cially if planted continuously to one 
crop like wheat) the nitrogen con- 
tent of the soil, the amount of moist- 
ure that it will contain, and the crop 
production are likewise decreased. 

All the methods for making poten- 
tial plant food available, which have 
been so far discussed, tend to de- 



crease the amount of humus in the 
soil. Tillage, drainage, bare-fallow- 
ing increase the amount of food avail- 
able to the crop because they pre- 
sent ideal conditions for the decom- 
position of the organic matter in the 
soil, a.nd dependence on these meth- 
ods alone will eventually result in in- 
jury through loss of humus. This fact 
is strikingly shown in the following 
table adapted from a Minnesota bulle- 
tin: 

Loss of Nitrogen and 
Humus From Soils. 
Cultivated 
Native Soil. 23 Years. 
Total humus 3.97 2.59 
Total nitro- 
gen .36 .19 

Capacity to 

hold water G2. 54. 

Phosphates 
with humus .07 .03 

The lesson to be learned from this 
table is that while intelligent use 
should be made of improved methods 
of tillage, etc., these should be sup- 
plemented by some means of main- 
taining the supply of humus. The 
method that first suggests itself is 
nature's own way of growing a crop 
to be afterwards incorporated with 
the soil. This is the process known 
as green manuring. "Plowing under 
green crops raised for that purpose 
is one of the oldest means of improv- 
ing the fertility of the soil. It was 
advocated by Roman writers more 
than two thousand years ago, and 
from that time until now has formed 
a most important resource of the 
farmer, especially where the supply 
of barnyard manure is insulficient. Its 
advantages are many. The more 
striking are that it furnishes the sur- 
face soil with a supply of fertilizing 
materials needed by the crop, in- 
creases the humus and improves the 
physical qualities and tilth of the 
soil. As a humus former green man- 
uring stands next to barnyard man- 
ure." (Farmer's Bulletin 16.) 

The value of green manuring de- 
pends primarily on the fact that it 
incpeases the amount of humus in 
the soil, a point that has been shown 
to be of great importance. The crops 
used for this purpose may be of two 
kinds, viz., those which add nothing 
directly to the soil and those which 
increase its nitrogen supply. Of the 



first class the crops generally recom- 
mended are, buckwheat, spurry, mus- 
tard, rye, rape, etc. Plowing sod 
land may be said to be a species of 
green manuring and as such would be 
included in this class. These crops, 
while they add no element of plant 
food to the soil are beneficial because 
they gather food that would not be 
available to the less hardy plants, 
and on their decay leave it in forms 
suitable to the succeeding crop. As 
mere humus formers they are of 
great value. 

The discovery that the leguminous 
plants can through the nodule form- 
ing bacteria fix the free nitrogen of 
the air, has thrown a new light on 
green manuring and the plants 
adapted to this purpose. The legumes 
have all the advantages of the other 
plants as humus formers and at the 
same time increase the amount of 
nitrogen in the soil. They are, as a 
rule, deeper rooted plants and are 
supposed to bring up mineral food 
from the subsoil and leave it where 
it will be within reach of the more 
shallow rooted plants. Of the le- 
gumes the crops most often recom- 
mended are red clover, cowpea, crim- 
son cloA^er. the lupines, soy bean, and 
the ordinary field bean, and field pea, 
red clover being probably the one 
most generally used. These plants 
have been found to produce good re- 
sults even when the crop was har- 
vested and the stubble only plowed 
under. At the Rothamsted Experi- 
ment Station it has been estimated 
that fifty pounds of nitrogen per acre 
is added to the soil in the roots and 
stubble of clover alone. 

Where it is not advisable to devote 
an entire season to the growth of a 
crop for green manuring, beneficial 
results may often be obtained by 
growing "catch crops" between the 
profit crops. The use of cover crops 
on orchards as a protection to the land 
during the winter is a mode of green 
manuring. As far as possible legum- 
inous plants should be used as green 
manures. One prominent agricul- 
tural investigator asserts that by 
good tillage and a judicious use of 
leguminous crops the fertility of the 
soil may be maintained indefinitely 
without the use of fertilizers of any 
kind. The writer feels that this 
point has yet tO' be demonstrated, but 
no one doubts that these plants are 



23 



of great value in the conservation of 
fertility. 

While green manuring is a valua- 
ble method of increasing the humus 
supply of the soil it is not unattended 
by danger. In a dry season, for in- 
stance, the growth of a crop to plov^r 
under may result in lowering the 
moisture content of the soil to a 
point that is detrimental to the suc- 
ceeding crop. There is also danger 
in such a season that there may not 
be sufficient moisture in the soil tc 
bring about the decomposition of the 
organic matter that is turned under, 
resulting in serious injury to the 
physical condition of the soil. If a 
crop is plowed under during a dry 
season the ground should be rolled or 
otherwise firmed so as to renew ca- 
pillarity as far as possible. 

Green manuring as a general prac- 
tice is not to be recommended in any 
style of stock farming. The crops 
which are most valuable as green 
manures are also of great value as 
feeds, and it will be found more 
profitable to feed them to the stock 
and return the manure to the field, 
as will be shown later. On the whole 
it may be said that green manuring 
will prove desirable in any system of 
farming (including truck farming) 
where the crops are sold from the 
farm, and especially if all the crops 
produced are much alike in their 
food requirements. On the other 
hand, if the farmer is engaged in 
animal husbandry the crops are of 
such great value as feeds that turn- 
ing them under must be considered a 
wasteful practice. 

(39) Rotation of Crops. — It is the 
common experience of farmers living 
in parts of the world where the land 
has been cultivated for a long time, 
that the fertility of the soil is main- 
tained for a much longer time by the 
growth of a variety of crops instead 
of producing one crop continuously. 
The adoption of a system of rotation 
of crops has been the outgrowth of 
accident rather than the result of an 
understanding of its underlying prin- 
ciples. The system of alternating 
years of bare-fallow and wheat may 
be said to be a two-year rotation and 
was the first to be adopted. History 
teaches us that this was later followed 
by a three-year rotation consisting of 
fallow, wheat, beans or oats; and still 
later, when the value of clover and 



fallow crops became evident, this ro- 
tation gave way to the now famous 
Norfolk rotation of turnips, barley, 
clover and wheat, the typical English, 
rotation. The Norfolk four-^year 
course represents the more common 
type of rotation the world over, con- 
sisting as it does of cereals alternat- 
ing with hoed crops and leguminous 
crops. 

There are many arguments to be ad- 
vanced in favor of growing a variety 
of crops on the land. The different 
plants vary in their food requirements 
and in their ability to procure this 
food from the soil. Where one crop 
is grown continuously on the same 
field nearly all of the plant food that 
is available to it may become ex- 
hausted, while the soil would contain 
large quantities of food in forms that 
could be assimilated by plants of an- 
other class. Some crops evidently re- 
quire the mineral matter to be in a 
readily soluble form, while others can 
use "tougher" forms of plant food. 
The early writers on agricultural 
chemistrj' supposed that the crop dur- 
ing its growth excreted substances 
that were injurious to itself, while 
they were at least harmless and per- 
haps beneficial to plants of a differ- 
ent class. This view is not now ac- 
cepted, but it is believed that the fail- 
ure to produce profitable results 
where one crop is grown continuously 
is due to the exhaustion of the forms 
of plant food available to that partic- 
ular crop. Some crops make an es- 
pecial drain on one element of plant 
food. By growing plants with differ- 
ent food requirements there is less 
likelihood of any one element becom- 
ing exhausted, and the different ele- 
ments are more evenly used. 

The various crops differ widely in 
their systems of root growth. Some 
plants like wheat are comparatively 
shallow rooted and must obtain their 
food from the surface soil. Others, as 
the clovers, are very deep rooted and 
are able to use food that would not 
be within reach of the more shallow 
rooted plants. The deep-rooted plants 
cannot only procure the low lying 
food, but probably bring a part of it 
to the surface, where it remains upon 
their decay for the use of the succeed- 
ing crop. It is well known that the 
shallow rooted plants do better when 
preceded by a deep rooted crop. 

When a variety of plants are grown 
the soil receives different treatment 



24 



for each crop, so that the faults of 
one year are likely to be corrected the 
next, and, for this reason, the soil is 
kept in much better physical condi- 
tion. As a general rule the ground 
can be better prepared for the suc- 
ceeding crop if a judicious rotation 
is practiced than if the same crop is 
grown continuously. The roots and 
stubble of clover and the grasses are 
also factors of some importance in 
improving the texture of the soil. 
Taken altogether the texture or tilth 
of the soil will be found to be much 
improved by rotation of crops. 

Where a variety of crops is grown 
on the farm it results in economy of 
labor, for the work of caring for them 
is distributed throughout the season 
instead of all coming at one time. In 
this way it makes it possible to secure 
cheaper and better help than where 
only a few kinds of plants are pro- 
duced. 

Rotation also enables the farmer to 
control plant diseases and to head off 
the injurious insects. Most of the 
plant diseases are caused by bacteria 
or other fungi which live only on one 
genus of plants, or, at any rate, are 
more or less restricted in the number 
of crops that they can use as host 
plants. Where one crop is grown 
continuously, these disease-producing 
fungi are given every opportunity to 
be carried over from one year to an- 
other. Most of these germs are com- 
paratively short lived, so that if three 
or four years of crops that are not 
suitable host plants intervene, these 
germs are likely to be destroyed. In 
the same way it may be said that the 
injurious insects are limited to cer- 
tain plants for their food supply, and 
if these plants are not grown on the 
field for a number of years the insects 
may die from starvation. These re- 
marks do not apply, of course, to those 
insects which have great migratory 
powers. There is no doubt, however, 
that both diseases and insects can be 
more easily suppressed if rotation is 
practiced. 

Rotation may be useful in destroy- 
ing weeds. "Certain classes of weeds 
infest certain kinds of crops much 
more than others; when this is the 
case, rotation may be made to do 
much to destroy them, by leaving the 
particular crop out of the rotation in 
which the weed or weeds appear. This 
is not difficult, since the ordinary crops 
of the farm are nearly equal in profit, 



if labor, use of the land, seed, and the 
amount of fertility carried to towa 
where the crop is sold, are all consid- 
ered. The farmer should study the 
undesirable plants quite as much as 
the desirable ones, that he may change 
or modify his practices so as to at- 
tack his enemies at their weakest 
points." (Roberts). 

The effect of rotation on crop pro- 
duction is strikingly shown in the fol- 
lov/ing table compiled from data fur- 
nished by the Rothamsted Experiment 
Station: 

EFFECT OF ROTATION OM CROP PRODUCTION 



Average of Eight Courses (32 Years.) 

I BUSHELS PER ACRE 



Grown 

continuously. , 

In rotation 



BARLEY 

18 



WHEAT 

12 

26 



The rotation was the Norfolk rota- 
tion, consisting of turnips, barley, 
clover and wheat, each grown one 
year, and the figures given are the 
average of eight crops each of barley 
and wheat, representing a period of 
thirty-two years. The experiments 
with v/heat and barley grown continu- 
ously on the same plot for fifty years 
have been previously mentioned. 
For the sake of comparison, the table 
gives the averages for the same eight 
years in which these crops were 
grown in the rotation. All the crops 
were harvested and removed from the 
field, and as no manure of any Idnd 
was used, it will be seen that the in- 
creased production of barley and 
wheat is a result of rotation solely. 
No stronger argument in favor of ro- 
tation of crops is necessary. 

Rotations are in use that cover 
periods of from two to seven or eight 
years. In planning a rotation the 
farmer must be guided by his own 
conditions and requirements in the 
way of crops. A few general rules 
may be laid down, however. Every 
rotation should include at least one 
cultivated or hoed crop, such as corn, 
potatoes, etc., in order to receive the 
benefits of such a crop in the way of 
destroying weeds, improving tilth, and 
setting free potential plant food. At 
least one leguminous crop should be 
included. The legumes are generally 
deep rooted crops, and in addition to 



increasing the nitrogen supply of the 
soil, bring up plant food from the sub- 
soil and leave it where it will be avail- 
able to the succeeding crop. These 
deep rooted plants render the subsoil 
more porous and hasten its disintegra- 
tion. A crop that is exacting in its 
food requirements should follow one 
that is less exacting, or in general 
terms the crops should vary as much 
as possible in their food requirements, 
manner of growth, root system, and 
the season of the year in which they 
occupy the ground. Whatever fertiliz- 
ers are used should be applied to the 
particular crop which will give the 
most profitable returns for its use. 

(40) Resume. — In Part I. the reader 
was reminded that continuous crop- 
ping without the use of fertilizers 
finally results in practical exhaustion 
of the soil. The food requirements of 
the plant and the history of the for- 
mation of the soil were briefly consid- 
ered, and the conclusion evolved was 
that to maintain the fertility of the 
soil two things were necessary: First, 
to make more of the potential food 
available; second, to add something to 



take the place of the materials re- 
moved in the crop. Part II. has been 
devoted to a discussion of the first 
proposition. Tillage, draining, irriga- 
tion, fallowing, green manuring and 
rotation are distinctly methods for 
changing potential plant food into 
available forms, and, with the excep- 
tion of the nitrogen gathered by the 
legumes, add no plant food whatever 
to the soil. Although, as has been 
previously stated, it is claimed by 
some that by an intelligent use of 
these processes alone a profitable 
yield can be obtained indefinitely, it 
is the common experience that even 
with the use of the best methods of 
culture known in the past, it is impos- 
sible to maintain the fertility of the 
land without the use of some form of 
fertilizers. As it is obviously impos- 
sible to return the crop to the soil, 
the next thing mat suggests itself is 
to feed the crop to farm animals and 
use their excrement as a fertilizer. 
The subject of barnyard manures is 
of sufficient importance to justify itsi 
discussion at some length as Part III. 
of this treatise. 



PART HI. Barnyard Manure. 



(40) Importance of Barnyard Ma- 
nure. — Barnyard manure is the oldest 
and is still undoubtedly the most pop- 
ular of all fertilizers. It has stood the 
test of long experience, and has proven 
its position as one of the most impor- 
tant manures. The fact that the ap- 
plication of the excrement of animals 
to the soil results in increased crop 
production, is mentioned by the early 
Roman writers, and from that time to 
the present, the majority of farmers 
have placed their main reliance on this 
class of manures for maintaining the 
fertility of the soil. 

"A well-kept manure heap may be 
safely taken as one of the surest in- 
dications of thrift and success in farm- 
ing. Neglect of this resource causes 
losses which, though little appreciated, 
are vast in extent. Waste of manure 
is either so common as to breed in- 
difference or so silent and hidden as 
to escape notice. 

According to recent statistics there 
are in the United States in round num- 
bers 19,500,000 horses, mules, etc., 61,- 
000.000 cattle, 47,000,000 hogs and 51,- 
600.000 sheep. Experiments indicate 
that if these animals were kept in 
stalls or pens throughout the year and 



the manure carefully saved, the ap- 
proximate value of the fertilizing con- 
stituents of the manure produced by 
each horse or mule annually would be 
$27, by each head of cattle $19, by each 
hog $12, and by each sheep $2. The 
fertilizing value of the manure pro- 
duced by the different classes of farm 
animals of the United States would, 
therefore, be for horses, mules, etc., 
$526,500,000; cattle, $159,000,000; hogs, 
$564,000,000; and sheep, $103,200,000, 
or a total of $2,352,700,000. 

These estimates are based on the 
values usually assigned to phosphoric 
acid, potash and nitrogen in commer- 
cial fertilizers and are possibly some- 
what too high from a practical stand- 
point. On the other hand, it must be 
borne in mind that no account is taken 
of the value of manure for improving 
the mechanical condition and drainage 
of soils, which as subsequent pages 
will shov/, is fully as important a con- 
sideration as its direct fertilizing 
value." (Farmers' Bulletin, 192). 

If it is assumed that one-third of 
the value of the manure is annually 
lost by careless methods of manage- 
ment, and this estimate is undoubtedly 
conservative, the total loss from this 



26 



source in the United States is about 
$750,900,000; a loss the more unfortun- 
ate because practically all of it could 
be prevented. 

(41) Composition of Manure from 
Different Animals. — The manures pro- 
duced by the various classes of ani- 
mals differ greatly in their composition 
and in their physical properties. The 
following table gives the average per- 
centage composition of the manures 
(including solid and liquid excrement) 
from the more common farm animals: 



AVERAGE COMPOSITION OF FRESH 

MANURES.— (Wolff.) 




PER CENT OF 




Water 


Nitro- 
gen 


Phos. 
Acid 


Potash 


Sheep manure.. 
Horse " 

PiST 

Cow 

Mixed Farm 
manures 


64.0 
70.0 
73.0 
77.0 

75,0 


0.83 
0.5S 
0.45 
0.44 

0.45 


0.23 
28 
19 
0.16 

0.21 


67 
9.53 
0.60 
0.40 

0.52 



Assuming that the fertilizing con- 
stituents of manure are equal in value 
to those found in commercial fertiliz- 
ers, the value of one ton of each of 
these manures is as follows: Sheep, 
$3.39; horse, $2.55; pig, $2.14; cow, 
$1.89; mixed, $2.08. (Note.— This val- 
uation is based on 15 cents per pound 
for nitrogen and 5 cents each for phos- 
phoric acid and potash. This repre- 
sents in round numbers the market 
price of these elements in commercial 
fertilizers at the present time. All the 
valuations given in the following pages 
will be on the same basis. The com- 
parative value of nitrogen, phosphoric 
acid and potash in barnyard manure 
and commercial fertilizers will be dis- 
cussed later). 

Referring to the table it is seen that 
the difference in the value of the ma- 
nures as given is due, to a large ex- 
tent, to the variation in the amount of 
water present in the excrement of the 
different classes of animals. The 
moisture content also affects the phy- 
sical properties of the manure. Ma- 
nures containing large amounts of 
water are "cold manures"; that is they 
are manures which heat slowly be- 
cause the amount of moisture present 
checks the fermentation. Sheep and 
horse manures are known as "hot ma- 
nures," and the more rapid heating of 
these when compared with pig or cow 
manure is probably largely due to their 
lower water content. The difference 



in the kind and quality of the feeds 
given to the various animals also af- 
fects the quality of the manure, as will 
be shown later. 

(42) Amount and Value of Manure 
from Different Animals. — The figures 
given in the previous section show the 
comparative fertilizing value of the dif- 
ferent animal excrements and are, 
therefore, of importance to one who is 
purchasing manures. For the farmer 
who produces manure to use on his 
own land, it is more important to know 
the total amount and value of the ma- 
nure produced in a year by the differ- 
ent classes of animals. In the quota- 
tion above from Farmers' Bulletin 192 
the approximate value of the manure 
produced per head by the ordinary 
farm animals is given. A fairer way 
to present the matter is to calculate 
the manure to the same live weight of 
the different animals. The following 
table compiled from Cornell Bulletin 
56 appears in Farmers' Bulletins 21 
and 192: 



Amount and Value pf Manurk Per 1,000 
Pounds of Live Wkight of Diffkrp;nt 

Animals. 



Sheep . 
Calves 
Hot's. . 
Cows . . 
Horses 



Amount 
Per Day 
Pounds 



34.1 

678 
83 8 
74.1 
48.8 



Value 

Per Day 

Cents 



6.7 
16.7 
8.0 
7.6 



Value 
Per Year 



f:6 nO 
24 45 
60 88 
28 27 
27 74 



This table shows that, with the ex- 
ception of the hog, the manure pro- 
duced from the same live weight of 
any of the animals is about equal in 
value. If the above figures are ac- 
cepted, one must conclude that the hog 
is over twice as valuable as the other 
animals as a manure producer. This 
statement is absurd on the face of it, 
and the above table is misleading. As 
this table has been widely copied, ap- 
pearing in several bulletins in this 
country and Canada as well as in a 
few text-books, it has unfortunately 
given rise to a widespread misconcep- 
tion of the value ot hog manure. The 
fact is that these figures do not repre- 
sent average conditions in the case of 
the hog as the animals used in the 
experiments from which the data were 
obtained were fed on an abnormal ra- 
tion. Three lots of pigs were used to 
obtain these averages and all were fed 
on rations containing an excessive 



27 



amount of protein to study the effect 
of high protein feeds on "the produc- 
tion of lean meat." In two cases about 
one-third of the dry feed in the ration 
consisted of "meat scrap obtained from 
the fertilizer manufacturers — and ap- 
parently composed of dried meat, blood 
and small pieces of bone. This meat 
scrap contained nearly 10 per cent of 
nitrogen." A nitrogen content of 10 
per cent means that the meat scrap 
contained 62i^ per cent of protein, 
and it is evident that the high value 
of the manure from 1,000 pounds live 
weight of hogs was due to the abnor- 
mal amount of protein in the ration, 
an amount that no one would think 
of using in practical feeding. In case 
of the other animals mentioned in the 
table, the rations were ordinary and 
the figures may be accepted as being 
approximately the average for good 
farm conditions. 

The writer has calculated the value 
of the manure from 1,000 pounds live 
weight of pigs, using as a basis of cal- 



of animals under farm conditions is 
practically the same irrespective of 
the kind of animal considered; and 
the sum of $25 may be taken as a con- 
servative estimate of the value of the 
fresh manure from each 1,000 pounds 
of live weight. The use of this factor 
($25 per 1,000 pounds) will enable the 
farmer to calculate approximately 
what the nitrogen, phosphoric acid and 
potash in the manure produced on his 
farm would cost if purchased in com- 
mercial fertilizers, granting that the 
manure is so managed as to prevent 
loss of its valuable constituents. 

(43) Value of tine Manure Deter- 
mined by the Ration. — The total value 
of the manure produced by a given 
number of animals is dependent on 
the quality and quantity of the feed- 
ing stuff used in the ration. That the 
different materials used for feeding 
vary greatly in their fertilizing value 
is clearly shown by the following ta- 
ble: 



FERTILIZING VALUE OF FEEDING STUFFS. (CORNELL BULLETIN.) 



Corn Meal 

Corn Silage. 

Crimson Clover (Green), 
Crimson Clover Hay ... 

Red Clover Hay 

Gluten Meal 

Cotton Seed Meal 

Linseed Meal 

Meat Scrap 

Wheat 

Skim Milk 

Oats 

Timothy Hay 

Wheat Bran 

Wheat Straw 

Turnips 



Value of 

Nitrog'en in 

one ton 



$ 4 S3 

78 

1 29 

6 63 
5 70 

15 09 
20 85 

16 08 
29 01 

7 08 
1 74 
5 36 
3 00 
7 56 

81 
48 



Value of 

Phos. Acid in 

one ton 



$0 83 
14 
16 
82 
54 
39 
3 66 

2 28 
6 01 

96 
26 
90 
43 

3 40 
30 
14 



Value of 

Potash in 

one ton 



$0 31 

32 

44 

2 26 

1 31 

OS 

1 65 

99 

67 

45 

1 08 

45 

1 17 

1 34 

1 02 

34 



Total 
Value 
per ton 



$ S 66 
1 24 

1 89 
9 71 

7 55 
IS S3 
26 16 
19 36 
35 69 

8 49 

2 11 
6 70 
4 60 

12 30 

2 18 

96 



eulation several rations recommended 
for practical use by recognized author- 
ities on feeding. According to these 
calculations the average value of the 
manure is a trifle under $30 per year, 
or approximately the same as that pro- 
duced by cows. In order that the table 
shall represent average conditions, this 
value should be substituted for that 
given for hogs. To sum up, it may be 
said that the average value of the ma- 
nure produced by a given live weight 



The figures given in the above table 
represent the fertilizing values of the 
different feeds provided they are used 
directly as manures. It is evident that 
the richer the ration is in nitrogen, 
phosphoric acid and potash, the more 
valuable will be the manure produced 
by the animal. The next question to 
determine is what proportion of the 
fertilizing content of the food is re- 
covered in the excrement. 

Let the reader imagine that a ma- 



28 



tured animal (a steer for instance) is 
confined in such a manner that all of 
the excrement, both liquid and solid, 
can be preserved, and that the ani- 
mal is kept on a maintenance ration. 
If now the total dry matter in the ma- 
terials fed is determined, and likewise 
that voided in the excrement, it will 
be found that the dry matter in the 
excrement is just about one-half the 
amount that was present in the food 
consumed, the greater part of the 
other one-half having been given off 
from the lungs as carbonic acid gas. 

If on the other hand the food is 
analyzed to determine the nitrogen, 
phosphoric acid and potash it con- 
tains, and the excreta are also exam- 
ined, it will be found that the entire 
amount of these constituents is voided 
by the animal in the solid and liquid 
excrement. While the excreta, there- 
fore, contain only half of the total dry 
matter which was present in the 
ration, it contains all of the constitu- 
ents that are generally considered to 
have fertilizing value. 

While these figures would hold good 
for a matured steer that was neither 
gaining or losing in weight they are 
not correct for young and growing an- 
imals. The latter retain a certain 
proportion of the nitrogen and phos- 
phoric acid for use in building up 
their bodies. The amount thus re- 
tained depends primarily on the age 
of the animal, and also as will be 
readily imagined, on the rapidity of 
its growth. Recent experiments indi- 
cate that calves during the first three 
months of their lives retain in their 
bodies about one-third of the fertiliz- 
ing value of the food consumed, or in 
other words, the excrement from such 
animals contains two-thirds of the fer- 
tilizing ingredients of the ration. For 
the first year of their existence they 
use in body growth an average of 
about one-fifth of the nitrogen, phos- 
phoric acid and potash that was pres- 
ent in the food, and the amount grad- 
ually diminishes until practically none 
of these materials are retained. It 
may be noted here that where matured 
animals are gaining in weight during 
fattening there is no drain on the fer- 
tilizing value of the manure provided 
the gain in weight is all in fat. This 
is due to the fact that fat contains 
only carbon, hydrogen and oxygen, 
and hence its production does not re- 
move any of those constituents which 
are considered in calculating the fer- 



tilizing value. Although the steer and 
calf have been used by way of illus- 
tration, the remarks regarding them 
hold true as well of the other classes 
of animals such as swine, sheep and 
horses, and the age of the animal has 
the same effect on the value of the 
manure. 

In the case of the cow another fac- 
tor is introduced, as a certain propor- 
tion of the nitrogen, phosphoric acid 
and potash is removed in the milk. 
Milk contains on an average about 
0.53 per cent of nitrogen. 0.19 per cent 
of phosphoric acid, and 0.175 per cent 
of potash. A cow giving an annual 
yield of five thousand pounds, there- 
fore, removes in the milk fertilizing 
materials amounting in value to $4.89. 
If the milk is sold, this amount of fer- 
tility is removed from the farm. If, 
on the other hand, butter only is sold, 
practically none is carried away, as all 
the valuable ingredients are found in 
the skim milk; the fertilizing value of 
three hundred pounds of butter, for 
instance, amounting to only &V2 cents. 
Even where the milk is removed, fully 
85 per cent of the manurial value of 
the food is recovered. 

It will thus be seen that a very 
large part of the elements of fertility 
contained in the ration fed is recov- 
ered in the excreta, and that the age 
of the animal is the principal factor 
in determining the amount that is re- 
moved. The fertility removed in the 
milk when it is sold from the farm 
is also of considerable importance and 
should not be ignored. Taking into 
account the ratio between matured 
and young stock, milch cows and non- 
milk-producing animals, as found on 
the average farm, it is conservative 
to assume that at least eighty (80) per 
cent of the nitrogen, phosphoric acid 
and potash present in the materials 
fed on the farm is voided by the ani- 
mals in the solid and liquid excre- 
ment. This takes into consideration 
the amount removed in the milk, that 
retained by the young animals during 
their growing period, and, conse- 
quently, the fertility removed from the 
farm by the sale of the animals pro- 
duced thereon. In order, then, to de- 
termine the fertilizing value of the ex- 
crement produced from a ton of any of 
the feeding stuffs mentioned in the ta- 
ble given above, it is only necessary 
to find 80 per cent of the fertilizing 
value therein stated. It will thus be 
readily seen that the composition of 



29 



the feeding stuff really determines the 
value of the excrement, that produced 
from one ton of wheat straw, for in- 
stance, being worth only $1.74, while 
the excrement from one ton of corn 
meal, wheat bran, linseed meal or cot- 
tonseed meal would be worth $4.53, 
$9.84, $15.49 and $20.93 respectively. 

By referring to the table it is seen 
that the most important factor in de- 
termining the fertilizing value of a 
feeding stuff or the manure produced 
from it, is the amount of nitrogen that 
it contains. This is due to the fact 
that nitrogen is usually present in 
larger proportions than phosphoric 
acid or potash and is much more costly 
when purchased. Nitrogen is also 
used by the animal body in much 
larger amounts than the other sub- 
stances, and the difference in fertiliz- 
ing value between the food and the 
excrement is largely due to the reten- 
tion of nitrogen. It will be shown that 
the losses in manure fall more heavily 
on its nitrogen content than on the 
other elements, so it again becomes 
evident that the most expensive ma- 
terial to furnish is also the one most 
readily lost. This but confirms a pre- 
vious statement that the problem of 
the profitable maintenance of fertility 
is largely a question of an economic 
method of supplying the plant with ni- 
trogen. 

While the total value of the excre- 
ment depends almost entirely on the 
composition of the ration, it does not 
follow that the value per ton of the 
manure is proportional to the fertiliz- 
ing value of the substances fed. Cat- 
tle fed on highly nitrogenous rations 
drink more water than those kept on 
a ration low in nitrogen, and experi- 
ments have shown that the excrement 
contains a larger per cent of water in 
the former case than in the latter. 
The cattle fed on the narrow ration, 
therefore, will produce more tons of 
excrement at a greater total value, 
but the value per ton will not be very 
different from that resulting from a 
wider ration. The following table 
adapted from a Cornell bulletin gives 
results with two lots of pigs; Lot I 
having been kept on feeds extremely 
high in nitrogen, while Lot II were 
given a ration containing a much 
smaller proportion of nitrogenous ma- 
terials. 



Excrement from 1000 Pounds Live 
Weight of Pigs. 



Lot 1. 

Lot 2. 



Wt. per 
day, lbs. 



108.9 
56.2 



Value 
per day 



fO.2106 

0.104 



Value 
per ton 



$3 86 
3 66 



It is noteworthy that while the to- 
tal value of the manure produced per 
thousand pounds of live animal in Lot 
I was twice that of Lot II, there is 
very little difference in the value per 
ton, due to the fact that the weight 
of excrement produced in the first 
case was nearly twice that in the lat- 
ter. 

(44) Effect of Bedding on Value of 
Manure. — The factors just discussed 
are those which affect the value of 
the excrement. The term barnyard 
manure as it is generally used in- 
cludes the excreta and the litter or 
bedding used to absorb the urine. 
The following table gives the compo- 
sition of some of the materials used 
for bedding. 

Fertilizing Constituents in One 
Ton of Litter. 



Potash 
lbs. 



Wheat fctraw 
Oat straw . . . 
Clover straw 

Sawdust 

Peat 



Nitro- 
gen 
lbs. 


Phos. 
Acid 
lbs. 


9.6 


4.4 


9.2 


5.6 


29.4 


8.4 


4.0 


6.0 


20.0 





12.6 

35.4 
25.2 
14.0 



It is evident that the total fertiliz- 
ing value of the manure is the sum of 
the values of the excrement and the 
bedding, and that the richer the bed- 
ding is in fertilizing constituents the 
more valuable will be the manure. 
The materials used for bedding are in 
most cases rather low in the elements 
of fertility so that the use of large 
amounts of bedding decreases the 
worth per ton of the manure, but in 
any case sufficient litter should be 
used to absorb all of the liquid excre- 
ment. 



30 



(45) Calculating the Amount of Ma- 
nure from the Ration. — It is often of 
great interest and importance to the 
farmer to be able to calculate approx- 
imately the amount of manure that 
will be produced from the materials 
fed to his animals, as well as its value. 
Various estimates of the amount of 
manure produced by the different 
classes of animals have been made 
from time to time, but it will be much 
more satisfactory to use the ration as 
a basis for calculation. The total 
weight of manure may be easily calcu- 
lated in this v/ay, and the figures de- 
rived are remarkably close to the aver- 
age results as determined by experi- 
ment. 

It has been stated that one-half or 
50 per cent of the dry matter present 
in the ration is recovered in the excre- 
ment. Experience has shown that the 
least amount of bedding that will ab- 
sorb all of the urine excreted by the 
animal must contain dry matter equal 
to one-fourth (25 per cent) of the dry 
matter in the feeding stuffs used. 
Therefore if it is assumed that just 
sufficient bedding is used to absorb all 
of the liquid excrement, it will be seen 
that the manure (excrement plus bed- 
ding) contains three-fourths (75 per 
cent) as much dry matter as was con- 
tained in the ration. According to the 
table in (41) mixed farm manures con- 
tain on the average 75 per cent of wa- 
ter or only 25 per cent of dry matter, 
so that the 75 per cent of dry matter 
mentioned above as occurring in the 
manure, must be multiplied by four 
to find the total weight of manure. 
This gives a result of 300 per cent of 
the dry matter in the ration for the 
weight of the manure produced there- 
from. It will thus be seen that to cal- 
culate the amount of manure resulting 
from the use of any given food materi- 
als it is only necessary to multiply the 
weight of the dry matter in the ration 
by three. This method of calculation 
can perhaps be made plainer by an ex- 
ample. Let it be assumed that a ra- 
tion is used which contains one hun- 
dred pounds (100 lbs.) of dry matter. 
The excrement produced by feeding 
this ration would contain fifty pounds 
of dry matter. In order to absorb all of 
the urine voided by the animay straw, 
or some other bedding material, must 
be used in an amount large enough to 
supply twenty-five pounds of dry mat- 



ter. Now as the manure is composed 
of the excrement plus the bedding, it 
follows that the manure contains 
seventy-five pounds of dry matter. 
Only 25 per cent of the manure is dry 
matter, so that the seventy-five pounds 
of dry matter in the example repre- 
sents one-fourth of the total weight of 
the manure. The manure, therefore, 
weighs 300 pounds, which is just three 
times the dry matter that was pres- 
ent in the ration assumed, 

This method of calculating the ma- 
nure by multiplying the dry matter in 
the ration by three holds true, of 
course, only when the theoretical 
amount of bedding is used. In actual 
practice the farmer uses all of the 
bedding materials he has at hand, even 
though in excess of the amount re- 
quired to absorb the urine; and it is 
generally considered to be advisable 
to do so, for the bedding materials de- 
cay much more readily when mixed 
with the excrement of animals. In the 
best farm practice, where the great- 
est possible use is made of all sub- 
stances suitable for feeding, there is 
seldom an excess of bedding materials. 
In case more litter than the theoreti- 
cal amount is used the method of cal- 
culation given above must be cor- 
rected by adding to the total the 
weight of the bedding in excess of 25 
per cent of the dry matter in the ra- 
tion. If in the example taken, for in- 
stance, instead of using twenty-five 
pounds of dry straw, fifty pounds had 
been used as bedding, the total weight 
of the manure would have been 325 
pounds. 

(46) Amount and Value of Manure 
From Fifty Cows. — The great value of 
barnyard manure as a farm resource is 
appreciated by very few farmers. Its 
importance is doubtless realized to a 
greater extent at the present time 
than ever before, but even now a 
large proportion of those engaged in 
agricultural pursuits seem to have lit- 
tle realization of the immense loss 
they are incurring by the waste of 
this important product of the farm. 
Indeed many farmers apparently look 
upon the manure as one of the neces- 
sary nuisances of a system of animal 
husbandry, and begrudge the time and 
labor required to remove it from the 
barn and feeding lot. Barns have 
even been known to be erected on the 
banks of swift running streams, with 



31 



the express purpose of emptying the 
manure into the creek, in order to 
have it removed with the least possi- 
ble expenditure of labor. While these 
cases are extreme, the reader has only 
to look around him as he travels 
through the country to see practices 
■which fall only a few degrees short of 
this in the matter of wastefulness, due 
either to lack of knowledge of the 
value of the manure or to an indiffer- 
ence that is even more lamentable 
than ignorance. 

In order that the great fertilizing 
value of the manure produced on the 
farm maj^ be more definitely shown, 
as well as to make clearer the meth- 
ods of calculation described in the pre- 
vious sections, the figures are given 
here for the food consumed and the 
amount and value of the manure pro- 
duced in one year by a herd of fifty 
dairy cows giving an average yield of 
fifteen pounds of milk daily. For the 
sake of simplifying the calculations 
and statements of results, it is as- 
sumed that the same ration is fed 
throughout the year. In actual prac- 
tice, of course, the ration varies some- 
what at different times of the year, 
but as the experienced feeder aims to 
keep approximately the same relation 
between concentrates and roughage, 
and, as nearly as may be. the same 
ratio between proteids and carbohy- 
drates, the results of this calculation 
from a single ration will not be very 
different from those which would be 
derived from a variety of rations each 
having about the same nutritive value. 

It is desired to make this estimate 
conservative, and for that reason no 
feeds are included in the ration that 
are unusually high in fertilizing con- 
stituents. The following ration will 
be used as a basis for the calculation: 

Daily ration for a cow weighing 
1,000 pounds and giving 15 pounds of 
milk per day: 

Ten pounds of a mixture of one- 
third each of cornmeal, ground oats 
and bran; 35 pounds of corn silage; 15 
pounds of clover hay (medium red). 

This combination has been recom- 
mended by a prominent authority on 
the feeding of animals as a good ra- 
tion for practical feeding, and one 
which will meet with the approval of 



conservative dairymen. At the same 
time the ration is well balanced and 
will conform reasonably well to the 
best feeding standards. A great many 
dairjTnen use a much higher feeding 
standard than is represented by this 
ration, and on the whole it may be 
said that the results of this calculation 
will be lower than the average for 
good dairy conditions. It will be as- 
sumed that just the amount of wheat 
straw which would theoretically be 
necessary to absorb the liquid excre- 
ment is used as bedding. 

The following table gives the dry 
matter and fertilizing constituents in 
1,000 pounds of the different mater- 
ials. 



Dry Matter and Fertilizing Con- 
stituents IN 1000 Pounds. 



Potash 

lbs. 



Cornmeal. 

Oats 

Bran 

Silage . . . , 
Clover , . . . 
Straw 



Dry 


Nitro- 


Phos. 


Matter 


gen 


Acid 


lbs. 


lbs. 


lbs. 


871. 


15.8 


6.3 


889. 


18.6 


7.7 


883. 


26.7 


28.9 


220. 


2.8 


1.1 


887. 


20.7 


3.8 


875. 


4.8 


2.2 



4.0 

5.9 
16 1 

3.7 
22.0 

6.3 



(Note. — Tables giving the amount of 
water and fertilizing constituents in 
each 1,000 pounds of all the ordinary 
substances used in feeding, or which 
are raised on the farm, can be found 
in a number of different books, among 
which may be mentioned Henry's 
"Feeds and Feeding," Woll's "Hand- 
book for Farmers and Dairymen," 
Robert's "Fertility of the Land," and 
"Yearbook of the U. S. Department 
of Agriculture"). 

The ration mentioned above repre- 
sents the amount of the different sub- 
stances fed to each cow per day. This 
amount must be multiplied by 50 and 
then by 365 to determine the total 
amount fed per year. From the to- 
tals thus obtained and by the use of 
the table just given it is possible to 
calculate the dry matter and fertiliz- 
ing constituents of the entire amount 
of food given to the fifty cows during 
the year. These results are compiled 
in the following table: 



32 



Tabi^e; Showing Total Amount of Materials Fed with Dry Matter and 
Fertilizing Constituents. 





Am't Fed 
Pounds 


Dry Matter 
Pounds 


Nitroyen 
Pounds 


Pbos. Acid 
Pounds 


Potash 
Pounds 


Cornmeal 

Oats 

Bran 


60830. 

60830. 

60830. 
638750. 
274250. 


52982.9 

54077.8 

53712.9 

140525.0 

239968.7 


967.11 
1141.34 
1624.16 
1788.50 
5676.88 


383.23 
468.39 

1757.98 
702.63 

1042.15 


243.32 
358.90 
979.36 


Silage 


2363.38 


Clover 


6033.50 






Totals 


1095490. 


541267.3 


11197.99 


4354 38 


9978.46 



While the totals given in the table 
shov/ the amounts of fertilizing con- 
stituents in the feeding stuffs used 
during the year, it will be remembered 
that only 80 per cent of this amount 
is recovered in the excrement. The 
solid and liquid excrement combined, 
therefore, contain of nitrogen 8,958.47 
pounds, phosphoric acid 3,483.50 
pounds, and potash 7,982.77 pounds. 

The manure, however, contains the 
fertilizing constituents of the bedding 
in addition to that found in the excre- 
ment. It has been stated that the 
least amount of bedding that will ab- 
sorb the urine must contain dry mat- 
ter equivalent to one-fourth the dry 
matter in the ration. The dry matter 
in the bedding used in this example, 
therefore, must amount to 135,316.8 
pounds. To furnish this quantity of 
dry matter it will be necessary to use 
at least 154,647.7 pounds of wheat 
straw. If the amounts of nitrogen, 
phosphoric acid and potash in this 
weight of straw are added to that in 
the excrement the results will express 
the quantities of these ingredients 
found in the manure. The following 
table gives these data: 



Fertilizing Constituents of the 
Manure. 





Nitrogen 
Pounds 


Phos. Acid 
Pounds 


Potash 
Pounds 


In excrement 
In bedding. . 


8958.47 
742.61 


3483.50 
340.22 


7982.77 
974.28 


Totals 


9701.08 


3823.72 


8957.05 



The prevaling prices of fertilizing 
materials at the present time, as given 
by the Eastern experiment stations, 



are such that the purchaser pays at 
the rate of 15 cents per pound for 
nitrogen, and 5 cents each for phos- 
phoric acid and potash. These prices 
hold only when crude materials are 
bought and much higher prices are 
paid for mixed fertilizers. To deter- 
mine the value of the manure pro- 
duced by the fifty cows it is only 
necessary to multiply the totals in the 
last table by the trade prices of the 
constituents. These calculations are 
given below: 

Value of Manure from 50 Cows. 

Value of nitrogen SI, 455 16 

Value of phosphoric acid 191 19 

Value of potash 447 85 

Total value of manure. . .52,094 20 

This means that the fresh manure 
from the fifty cows would contain 
amounts of nitrogen, phosphoric acid 
and potash that would cost the farmer 
at least $2,094.22 if purchased in com- 
mercial fertilizers. How nearly the 
actual agricultural value of the manure 
will approach the trade value depends 
on a number of conditions, such as the 
crop to be fed, the physical condition 
and tilth of the soil, the climatic con- 
ditions, and above all the intelligence 
displayed in its care and use. The 
same statements apply, however, to 
commercial fertilizers, the trade 
price not necessarily being any indi- 
cation of the agricultural value of the 
material, and there is no doubt that 
the farmer who receives the best re- 
turns from commercial fertilizers is 
also the one who will be best repaid 
for the use of barnyard manure. What- 
ever the reader's opinion may be of 
the actual value of manure, the figures 
evolved in this calculation should im- 
press him with the fact that his ma- 



33 



nure heap is a valuable resource, and 
that he cannot afford to waste so val- 
uable a substance even if it is but a 
by-product of the farm. 

It will be interesting to carry these 
calculations a little farther and deter- 
mine the total amount of manure pro- 
duced and the value per ton. It has 
been shown that the weight of the 
manure is three times the weight of 
the dry matter in the ration. The to- 
tal dry matter fed during the year was 
found to be 541,267.3 pounds, so the 
manure would weigh 1,623,801.9 
pounds, or 811.9 tons. The total value 
of the manure divided by the number 
of tons gives $2.58 as the value of a 
ton of the manure. 

As was stated in the beginning of 
this section, this ration is considered 
a conservative one. The writer has 
made a few calculations from rations 
in use by practical dairymen that have 
run from five to six hundred dollars 
higher per year for fifty cows than 
does the one used in this example. 

The easiest way for the farmer to 
calculate the value of the manure pro- 
duced per year on his farm is to add 
together the amounts of fertilizing 
constituents in all the foods fed to the 
various animals; take 80 per cent, of 
this and add to it the fertilizing con- 
stituents of the bedding, and multiply 
the total by the trade prices per pound 
given above. If the reader will take 
the trouble to do this for his own farm 
he will find the results extremely in- 
teresting, and will be well repaid for 
his labor in the better understanding 
that he will have of his farm re- 
sources. 

(47) Relation of Manure to Main- 
tenance of Fertility. — The discovery 
of the fact that fully eighty per cent, 
of the fertilizing constituents of the 
crop can be recovered in the manure, 
has thrown a new light on the subject 
of the maintenance of fertility. A 
number of the most prominent author- 
ities on agricultural chemistry believe 
(and the belief seems perfectly 
plausible in view of the facts already 
discussed) that in a system of strictly 
animal husbandry, where nothing is 
sold from the farm except animals or 
animal products, the fertility of the 
soil may be maintained indefinitely 
without the purchase of fertilizers, 
provided the manure is properly util- 
ized. This assumes, of course, that as 
nearly as possible the full value of the 



fresh manure is realized and that the 
losses, which are to be discussed later, 
are avoided. Not only may the fertil- 
ity be maintained in this way, but it 
may actually be increased, as has 
been demonstrated by a number of 
farmers. 

It has been shown that where the 
crop is allowed to remain on the 
ground to decay and become a part of 
the soil, the fertility of the land in- 
creases from year to j^ear. The fact 
was also brought out that the soil 
contains large quantities of potential 
plant food, especially of the mineral 
elements, and that each year a certain 
portion of this potential food is be- 
coming available. The question that 
suggests itself is whether the food 
rendered available each year is suffi- 
cient to make up for the twenty per 
cent, loss in feeding the crops to ani- 
mals. There seems to be no reason to 
doubt that this is so in case of the 
mineral elements even if not true of 
nitrogen. The twenty per cent, loss in 
feeding falls nearly altogether in the 
nitrogen, while very little of the phos- 
phoric acid and potash are lost; so 
that it is easy to realize that the sup- 
ply of these two elements can be 
maintained by the use of the manure 
and a good system of tillage. The ex- 
periments at Rothamsted indicate that 
the growth of a crop of clover adds 
from fifty to seventy-five pounds of 
nitrogen per acre to the soil, 
and consequently this suggests a 
method of replacing the nitro- 
gen lost through feeding. Taking 
all things into consideration it is evi- 
dent that under the conditions men- 
tioned above it is possible to keep a 
farm fertile indefinitely through the 
use of the barnyard manure produced 
on it, supplemented by good tillage 
and the growth of leguminous crops. 
This statement holds true only where 
no crop is sold. In case the crop is 
sold the entire amount of fertilizing 
ingredients that it contains is re- 
moved from the farm. Where the 
farmer depends for his profit on the 
sale of animals and animal products, 
however, there is no doubt that the 
fertility can be maintained in the man- 
ner described. 

(48) How to Increase the Value of 
the Manure. — It often occurs that the 
farmer finds it necessary, for one rea- 
son or another, to supply more plant 
food to the soil than can be obtained 
from the manure produced from the 



34 



crops raised on his farm. Under these 
circumstances if he is engaged in ani- 
mal husbandry he will find that the 
most economical way to increase the 
plant food is by purchasing feeding 
stuffs rich in the fertilizing constitu- 
ents, feeding them to his animals and 
using the manure as a fertilizer. The 
most successful stockmen find it 
profitable to reinforce the feeds raised 
on the farm with one or more of the 
various mill products and other by- 
products that are sold as cattle feeds. 
A glance at the table in (43) will im- 
mediately suggest how easily the 
value of the manure might be in- 
creased at the same time that the ra- 
tion was being materially improved. 
It will be readily seen that the pur- 
chase of a relatively small quantity of 
some of the concentrated feeding 
stuffs would more than replace the 
twenty per cent, of fertilizing value 
of the crops which is lost during feed- 
ing. The farmer who buys large quan- 
tities of concentrates is increasing the 
fertility of his land rapidly, provided 
he is taking proper care of the ma- 
nure. 

In purchasing feeding stuffs one 
should always consider their fertiliz- 
ing value as well as the feeding value, 
for while the substance is bought pri- 
marily for its feeding value it is some- 
times possible to buy two different 
materials, which will serve practically 
the same use as feeds and yet vary 
greatly in their values as fertilizers. 
Right here the reader should be 
warned against the reports of experi- 
ments where the value of the manure 
is considered in calculating the profit 
from feeding. A feeding experiment 
that does not show a profit in the in- 
crease alone, without taking the ma- 
nure into account, cannot be consid- 
ered very successful. The business 
farmer expects to make a profit on all 
the feeding stuffs used by increase in 
weight of his animals, in dairy prod- 
ucts or in some other salable product 
and, if he is not doing that, it is time 
for him to change his methods. As 
long as the feeder can buy feeding 
stuffs and sell his products at a profit 
on the investment it is good business 
policy for him to do so, but his profit 
should be a tangible one and not exist 
only in the manure heap. In other 
words the manure is distinctly a by- 
product of the farm and costs the 
farmer practically nothing, but the 
fact that it is a by-product does not 



make it less valuable. Good business 
policy demands that the manure heap 
be as well cared for as if it repre- 
sented an actual cash outlay equal to 
that which would be required to pur- 
chase its fertilizing equivalent in com- 
mercial fertilizers. Even where a 
number of animals sufficient to con- 
sume all of the crops raised on the 
farm are at hand it is often advisable 
to sell some of the products and use 
the money thus obtained for the pur- 
chase of other feeding stuffs. There 
is scarcely a farm on which such an 
exchange could not be made to ad- 
vantage, both from the feeding stand- 
point and in order to increase the 
value of the manure. A study of the 
market prices of the various farm 
products and concentrates in any year 
will readily show how such exchanges 
could be made at a profit to the 
farmer. To illustrate what is meant 
by this statement the following sim- 
ple example used recently by the 
writer in one of his classes is given. 

At the time mentioned it was possi- 
ble to buy on the local market seven 
tons of clover hay for the price of five 
tons of timothy hay, and five tons of 
corn could have been exchanged for 
six tons of bran. The problem was to 
determine the increase in fertilizing 
value due to such an exchange. Cal- 
culating the value of the different 
materials in the manner already de- 
scribed the results may be briefly 
stated as follows: 

Fertilizing- value of 7 tons of clover $52.85 

Fertilizing- value of 6 tons of bran "3.80 

Total $126.65 

Fertilizing- value of 5 tons of timothy. . . $23.00 

Fertilizing value of 5 tons of corn 28.30 

Total $51-30 

Gain due to exchange $75.35 

By a simple exchange of products 
without any cash outlay the fertilizing 
value of the ration would have been 
increased $75.35 and consequently the 
manure produced would have been 
worth $60.28 more than that resulting 
from the use of the corn and timothy 
hay. The increase in value of the 
manure does not tell all of the story, 
for the total weight of food has been 
increased nearly one-third. Its actual 
feeding value has increased more 
than one-third, due to the larger 
amount of protein in the ration. It is 
well known that cattle require less 
weight per head of a narrow ration 
than of one that is more carbonaceous. 



35 



This example is cited merely as a 
suggestion of the possibilities of ex- 
change. A little careful consideration 
will show that such exchanges may be 
made of great practical value. 

The value of the manure is affected 
by the quantity of food given the ani- 
mal as well as by the quality. Other 
things being equal, the manure from 
animals fed liberally will be more val- 
uable than that from those that are 
fed insufficiently. This is mainly due 
to the fact that the latter use a larger 
proportion of the nitrogen of the food 
and hence the per cent, returned in 
the manure is smaller. Liberal feed- 
ing, then, produces richer manure. 

(49) Relative Value of Liquid and 
Solid Excrement. — The values given 
for manures refer only to fresh ma- 
nures that have been handled so as 
to prevent loss of any kind. The 
greatest loss that is likely to occur is 
due to the waste of the liquid excre- 
ment through the use of insufficient 
bedding to absorb it. The urine is 
really the most valuable part of the 
excrement and unless plenty of bed- 
ding is used the value of the manure 
will fall far below that given in the 
previous discussions. Apparently but 
few people realize the importance of 
using plenty of litter, for it is not un- 
usual to see barns constructed in such 
a way as to cause the urine to run off 
as rapidly as possible. Doubtless the 
reader has before now seen holes 
bored in the barn floor to keep the 
floor dry by draining off the liquid 
excrement. The following table gives 
the composition of the solid and liquid 
excrements : 

Nitrogreu Phos. Acid ^potath'^ 

Sol. Liq. Sol. Liq. Sol. Zdq. 

norses 0.50 1.20 0.35 trace 0.30 1.50 

Cows 0.30 0.80 0.25 " 0.10 1.40 

Swine 0.60 0.30 0.45 0.125 0.50 0.2 

Sheep 0.75 1.40 0.60 0.05 0.30 2.0 

The table shows that, considered 
pound for pound, the liquid excrement 
is more valuable than the solid, except 
in the case of the swine. As the rela- 
tive weights of solid and liquid excre- 
ment produced by the animals are not 
given it does not show the real pro- 
portional value of the liquid and solid 
excrement produced from a given ra- 
tion. Several experiments have been 
made to determine this point and 
there is a wide variation in the re- 
sults. It is perfectly safe to say, how- 
ever, that of the total fertilizing ma- 
terials found in the manure sixty per 



cent, of the nitrogen, fifty per cent, of 
the potash and practically none of the 
phosphoric acid are found in the urine. 
The solid part then contains only 
forty per cent, of the nitrogen, half 
of the potash and nearly all of the 
phosphoric acid. It will thus be seen 
that a little over half of the total value 
of the manure is in the urine. In the 
example mentioned in (46) if the 
liquid excrement had been allowed to 
run away the value of the manure 
would have been under $1,000.00 in- 
stead of $2,049.00 as calculated. 

This last statement does not prop- 
erly show the comparative value of 
the solid and liquid parts of the ma- 
nure. The plant food in the urine is 
in a form that is soluble in water and 
consequently much more readily avail- 
able to the plants than that in the 
solid excrement. The solid excrement 
consists of the undigested portion of 
the food and must undergo thorough 
decay before its fertilizing constitu- 
ents become available to the plants, 
so that while only about half of the 
actual plant food is in the urine, the 
value of the urine is much greater 
than the dung owing to the better con- 
dition of its plant food. The differ- 
ence is due largely to the more avail- 
able form in which the nitrogen ex- 
ists in the urine. 

That the difference in value of solid 
and liquid excrement is not wholly 
theoretical is shown very nicely by 
a New Jersey experiment. In this ex- 
periment two plots were treated with 
manure, in one case the solid excre- 
ment only was used, while in the other 
the mixed solid and liquid excrements 
were used. Each plot received 
enough of the manure to supply ex- 
actly the same amount of nitrogen, 
and the other elements were added 
in excess. The results are stated in 
per cent, of gain over a check plot 
that received no manure and are 
given below: 

Pkr Cent. Gain in Yield from Manure. 
Solid E-^cre- Solid and 
meiit Only. Liquid. 

First year 15.2 52 7 

Second year 69.7 116.9 

Third year 47.9 80.6 

Averag-e 44.3 83.4 

It will be seen that the yield from 
the same amount of nitrogen was very 
much larger from the mixed manure 
than from the solid excrement alone. 
It is evident that the first and perhaps 
36 



most important requirement to ob- 
tain the full value of the excrement 
is to provide plenty of material to ab- 
sorb all of the urine and prevent any 
of it being wasted. It may be said 
here that where bedding material is 
scarce it can be made to go farther 
by running it through the cutter. 
Straw cut into one inch lengths, for 
instance, will absorb about three 
times as much urine as long straw. 

(50) Losses in Manure. — The great 
possibilities of barnyard manure as a 
means of supplying nitrogen, phos- 
phoric acid and potash to the soil have 
been discussed at some length. While 
values equal to those mentioned may 
be realized by any farmer by the ex- 
ercise of reasonable care, the fact re- 
mains that few even approximate 
these results with their present prac- 
tices. Barnyard manure is a perish- 
able material and must be handled 
with care and intelligence to obtain 
its maximum value. As manure is 
managed on the majority of farms to- 
day, it is doubtful if more than half 
its worth is realized. 

Before discussing the methods of 
preservation of manure it will be well 
to indicate some of the sources of 
loss. One of the principal causes of 
loss in value in manure is the faulty 
construction of stables and the use of 
insufficient bedding. Stable floors 
should be so tightly constructed that 
it is impossible for the liquid excre- 
ment to drain away. In spite of the 
fact that so much has been written 
about the fertilizing value of the urine 
of animals, there seems to be little 
attempt on the part of most farmers 
to preserve all of the liquid excre- 
ment. It has been shown that more 
than one-half the total value of the 
excrement is in the urine, and the 
man who does not strive to prevent 
its loss has not yet realized the great 
value of this substance. It is not 
enough to have tight floors, but bed- 
ding should be used in such quantities 
that the manure can be easily removed 
from the barn without loss of the 
liquid excrement; that is, the urine 
should be so thoroughly absorbed that 
there will be no drip in handling the 
manure. 

Manure is never so valuable as when 
perfectly fresh. The very best meth- 
ods of handling and care, if the ma- 
nure is stored, cannot prevent more 



or less loss of the valuable constitu- 
ents. For this reason it is advisable 
when possible to apply the manure to 
the soil as fast as it is made, a point 
that will be discussed at some length 
later. 

Next to improper absorption of the 
urine the greatest loss in manure 
comes from leaching by rains. As or- 
dinarily handled the manure each day 
is thrown out into the open yard to 
lie for months, subject to washing by 
the summer or winter rains. In many 
cases it is even deposited directly un- 
der the eaves of a large barn, so as to 
make the washing process the more 
complete. It seems absurd to go to 
the trouble of absorbing all the liquid 
excrement by means of bedding and 
then allow it to be washed out of the 
manure by the rains, and yet that is 
what very often occurs. The losses in 
manure due to leaching by rains in 
the open yard are much greater than 
most people imagine. Many experi- 
ments have been carried on to illus- 
trate these losses, but the limits of 
this paper will permit the presenting 
in detail of only one or two of them. 

At the New Jersey Experiment Sta- 
tion four samples of manure were ex- 
posed to the weather for varying peri- 
ods and the loss of fertilizing constitu- 
ents determined. The results are sum- 
marized in the following table: 

Losses in Manure. 



Period 


Nitrog-en 
Per cent. 


Phosphor- 
ic Acid 
Per cent. 


Potash 
Per cent. 


131 Days.. 

70 " . 
76 " . . 

50 " . . 


57. 
44. 
39. 
69. 


62. 
16. 
63. 
59. 


72. 
28. 
56. 

72. 


Average. 


51.0 


51.1 


61.1 



It will be seen that the average 
loss amounted to more than half the 
value of the manure during rather 
short periods, the longest time being 
a trifle over four months. On many 
farms the manure is exposed to the 
elements for a much longer period 
than that given in the table. 

In 1890 experiments were conducted 
at Cornell with manure exposed to the 
weather for a period of five months 
(from April to September), with the 
following results: 



37 



Horse manure. 
Cow manure . . 



Value 
per ton 

at be- 
ginning' 



P. 80 
2.29 



Loss 
Per Ton 



1.74 
.69 



Losses in Solid Excrement. 



Loss 
Per Ct. 



62.0 
30.0 



Tests at the Canada Experiment 
Farm with horse manure exposed to 
the weather for six months showed a 
loss of one-third of the nitrogen, one- 
sixth of the phosphoric acid and one- 
third of the potash, while a corre- 
sponding sample that was protected 
from the weather lost only one-fifth 
of its nitrogen and none of the phos- 
phoric acid or potash. 

Examples similar to these might be 
given indefinitely from American and 
European experiments did space per- 
mit. It is only necessary to state 
here that all of these experiments 
show great losses in the valuable con- 
stituents of the manure from exposure 
to the elements, the decrease in value 
amounting to from 30 to 70 per cent 
for periods of three to twelve months. 
These losses vary with the climatic 
conditions and with the quality of the 
rations. During heavy rains, especi- 
ally if occurring in warm weather, the 
losses will be much greater than in 
dry or cold weather. The relative de- 
crease in value is larger for manures 
produced from rations of high nutri- 
tive value. In other words the more 
valuable the manure the greater will 
be the per cent of loss from leaching. 
It is conservative to say that manure 
exposed to the weather for six months 
loses fully half its value. It is not 
the liquid excrement alone that is 
washed away by the rains, for the 
solid excrement contains a certain 
amount of soluble plant food which is 
removed by leaching. In addition to 
this there are chemical changes taking 
place in the manure which are con- 
verting some of the constituents, 
which were originally insoluble, into 
forms that are soluble in water, and 
these may be carried away by the 
rains. Below are given the results of 
experiments at New Jersey to deter- 
mine the losses due to leaching when 
the solid excrement alone was con- 
sidered: 



Period 


Nitrogen 
Per cent. 


Phosphor- 
ic Acid 
Per cent. 


Potash 
Per cent. 


131 Days.. 
70 " .. 

76 " .. 
50 " . 


46. 

34. 
25. 
45. 


73. 
27. 
54. 
42. 


80. 
10. 
48. 
42. 


Averag-e. 


37.6 


51.9 


47.1 



The figures given in the above ta- 
bles representing the percentage loss 
of fertilizing constituents from the ma- 
nure, do not tell the whole story. The 
nitrogen in the portion removed by 
leaching is more valuable per pound 
than that which remains because it is 
in a form more immediately available 
to the crop. This fact is strikingly 
shown in an experiment conducted at 
the New Jersey Station in which two 
plots were treated with amounts of 
fresh and leached manures that would 
give exactly the same amount of ni- 
trogen. The results stated in per 
cent of gain over a plot receiving no 
manure are given below: 

Per Cent. Gain in Yield from Manure 





Fresh 
Manure 


Leached 
Manure 


First Year 

Second Year 

Third Year 


52.7 
180.4 
117.5 


41.5 
96.8 
89.6 


Averag-e 


116.9 


76.0 



On perhaps a majority of the farms 
in America the cattle are fed during 
the winter in open lots, the manure 
not being hauled away until the fol- 
lowing summer or fall, if indeed It is 
removed at all. This method of feed- 
ing presents ideal conditions for ex- 
cessive losses from leaching, and it 
is safe to say that more than half the 
fertilizing value of the manure is lost 
where this practice is pursued. In the 
"corn belt" of Ohio, for instance, large 
numbers of cattle are fed during the 
winter and it is not unusual to see 
a large feeding lot covered to a con- 
siderable depth with manure which is 
spread out and exposed to the weather 
in such a way that the maximum ef- 
fects of leaching must take place. 
There is no doubt that, considered 
from the fertility point of view alone, 
the farm would be better off if the 



38 



corn were sold from the farm and the 
stover all plowed under. To illustrate 
what is meant by this statement, the 
writer quotes from a letter of inquiry 
recently received by him and his re- 
ply to the same. The query, "The 
method of cattle feeding followed by 
many farmers in this country is to 
feed in an open lot which frequently 
has not even a strawstack for wind 
protection, all being exposed to the 
rain. When they have their cattle on 
full feed they think they feed about 
one-half bushel of corn per day, the 
most of them allowing the stover to 
go with the corn to be wasted — since 
a steer on full feed will not eat so 
much stover. Assuming a yield of 
fifty bushels of corn per acre and 
about R.500 pounds of corn stover per 
acre fed to cattle, how, in detail, would 
the manure which was hauled from 
this feed lot in the following July com- 
pare in chemical constituents with the 
corn stover if left on the field?" 

Answer — "Your acre of corn stover 
(3,500 pounds) would contain 36.40 
pounds of nitrogen, 49.9 of potash and 
10.15 of phosphoric acid. Putting the 
cost of nitrogen at 15 cents per pound 
and potash and phosphoric acid at 5 
cents per pound each (just about 
trade values for this year), the value 
of the stover as a fertilizer would 
amount to 8.42 dollars per acre. The 
soil would get all of this if the stover 
was not removed from the field. 

"Fifty bushels (3,400 pounds) of ear 
corn contains 47.94 pounds of nitro- 
gen, 15.98 pounds of potash and 19.38 
pounds of phosphoric acid, which at 
above prices would give 8.96 dollars 
for the fertilizing value of one acre 
of ear corn. 

"From this it follows that the total 
fertilizing value of the crop is 17.38 
dollars, i. e., if the entire crop was 
plowed under it would add to the soil 
amounts of nitrogen, potash and phos- 
phoric acid that would cost 17.38 dol- 
lars if purchased in commercial fer- 
tilizers, or, of course, would remove 
the same amount from the soil if the 
entire crop was harvested. 

"In feeding a crop we estimate that 
under ideal conditions about 80 per 
cent of the fertilizing ingredients can 
be recovered — the other 20 per cent 
being utilized to build up animal tis- 
sue, etc. This figure varies with the 
class of animals fed, i. e., the more 
mature the animals the less the loss. 



while with young and growing ani- 
mals the loss is greater. The above 
figure pretty well represents average 
conditions, however. This means that 
under ideal conditions we could pro- 
duce manure equal to 13.90 dollars per 
acre from the corn crop. 

"A number of experiments have 
been conducted to show the losses in 
manures under just such conditions as 
you describe, and they have nearly all 
been carried on for about the length 
of time mentioned by you (about six 
months). These experiments show 
losses in fertilizing value in the ma- 
nure amounting to from 40 to 60 per 
cent of the total original value, the 
average being about 50 per cent. The 
manure produced from one acre of 
corn is worth at the time of hauling 
out only half the ideal value given 
above, or 6.95 dollars, leaving a bal- 
ance in favor of the stover alone (if 
left standing in the field) of 1.47 dol- 
lars, not to say anything of the labor 
of hauling the two ways. This refers 
to the fertility side of the question 
alone and takes no acount of the feed- 
ing value. On general principles it 
may be said that any crop or portion 
of a crop that cannot be used to feed 
had better be left in the field." 

There is another source of loss in 
stored manure that may be quite as 
wasteful as leaching, i. e., what is 
known as "hot fermentation." Ma- 
nure is very easily decomposed and 
there is no doubt that decomposition 
begins almost as soon as the excre- 
ment is voided by the animal. The 
first evidence of decomposition or fer- 
mentation is the odor of ammonia 
that is noticeable in the barn, espe- 
cially in the morning, if the stable has 
been closed during the night. This 
is due to rapid decomposition of urea, 
a nitrogenous substance found in the 
urine. Ammonia contains nitrogen, 
a.nd v/hen its odor is perceptible it is 
a sign that nitrogen is being given off 
into the air and that the manure, 
therefore, is undergoing a loss of this 
valuable constituent. The early de- 
composition of the urea will not be 
so likely to occur if plenty of absorb- 
ing material is used. 

The fermentation of manure is due 
to different forms of bacteria. Some 
of these germs can exist only in the 
presence of oxygen and are called 
"aerobic" bacteria, while others do not 
require free oxygen and are desig- 



39 



nated as "anaerobic" bacteria. It is 
the aerobic organisms that cause the 
hot fermentation which is the cause 
of great loss of value in manure. It 
is well known that if manure is thrown 
loosely into a heap, especially if it 
contains large quantites of horse or 
sheep excrement, it soon becomes very 
hot and dry, "fire-fanged," as it is pop- 
ularly termed. During this process 
large losses of nitrogen are occurring. 
Experiments conducted to show the 
loss due to fermentation alone indi- 
cate that from 30 to 80 per cent of the 
nitrogen is removed, but that the phos- 
phoric acid and potash are not affect- 
ed. In the case of the fire-fanged ma- 
terial, in one experiment it was found 
that all of the nitrogen was lost. As 
the value of manure depends for the 
most part on the nitrogen content, it 
follows that more than half its worth 
may be lost by hot fermentation. 

If the manure heap is so compact 
that the air cannot penetrate it the 
aerobic bacteria are unable to live and 
hence hot fermentation is not possi- 
ble. The presence of a large quantity 
of water also checks this kind of de- 
composition, and for that reason the 
excrement of cows and pigs is not so 
linble to hot fermentation as is that 
of horses and sheep. 

Where the manure is in a compact 
mass the fermentations that take place 
are due to the anaerobic organisms. 
These bacteria cause decompositions 
in the manure which convert the in- 
soluble plant food in the excrement 
into soluble forms, but do so with lit- 
tle loss of the fertilizing constituents 
provided the heap is protected from 
leaching rains. Even under the best 
of conditions it is not possible to en- 
tirely eliminate losses in stored ma- 
nure, although if properly preserved 
the loss may be limited to about 10 
per cent of the nitrogen and none of 
the other two constituents. This 
loss, however, is insignificant in com- 
parison with the losses which result 
from not saving the urine, from leach- 
ing due to rains, or from allowing the 
manure to undergo hot fermentations, 
all of which waste may be controlled 
to a great extent, as will be shown 
under the next heading. 

(51) Preservation of Manure. — The 
great value of the manure produced on 
the farm, and the losses that may 
occur in it, have been discussed at 
some length. The next point to be 



considered is the best method of car- 
ing for manure so as to prevent these 
losses as far as possible. Much that 
will be said under this heading has 
undoubtedly been already suggested to 
the reader by his perusal of the previ- 
ous sections, but the subject is of suf- 
ficient importance to justify devoting 
some space to it, even though repeti- 
tion becomes necessary. 

Attention has been called to the fact 
that over one-half of the value of the 
manure is in the liquid excrement, and 
it is desired to emphasize the state- 
ment that the first consideration in 
caring for manure is to have that part 
of the barn floor upon which the ex- 
crement falls so tight that none of the 
liquid can seep through. The manure 
trough behind the cattle, especially, 
should be made absolutely tight by the 
use of pitch, cement or some other ma- 
terial that is impervious to water. In 
addition to this, care should be used 
to supply litter in quantities large 
enough to absorb the urine so thor- 
oughly that the manure may be re- 
moved without loss from dripping. If 
the farmer possesses a feed cutter, he 
will be well repaid for cutting up all 
of the bedding materials, not only, be- 
cause this increases the absorptive 
power, but because the manure is so 
much more easily handled. Prominent 
stockmen have asserted that the 
greater ease with which manure con- 
taining short bedding can be handled 
and spread, well repays the cost and 
trouble of cutting all the litter, to say 
nothing of the saving in bedding mate- 
rials, and the latter is an important 
item on a farm that is stocked to its 
full capacity. 

Most of the nitrogen present in the 
urine exists in the compound known 
as urea. This is very readily decom- 
posed by bacteria and changed into a 
compound of ammonia and carbonic 
acid known as "carbonate of am- 
monia." This substance is volatile, 
and is sometimes given off into the air 
in such quantities as to be readily de- 
tected by the nose (i. e., by the odor 
of ammonia.) This kind of decomposi- 
tion takes place more readily in horse 
and sheep manures than in that from 
cattle or swine, as anyone can testify 
who has taken care of these animals 
when confined in closed barns. No 
doubt the reader has gone into the 
horse barn on a winter morning when 
there was so much ammonia in the 
air that it "made the eyes water." 



40 



When the odor of ammonia is percepti- 
ble it means that nitrogen is being 
given off from the manure, and the 
loss from this source may be an item 
of considerable importance. This loss 
may be prevented to some extent by 
the use of gypsum or land-plaster. The 
addition of this substance to a solu- 
tion of carbonate of ammonia brings 
about a chemical change that converts 
the ammonia into a compound that is 
not volatile, and hence does not pass 
off into the air; and at the same time 
the gypsum increases the value of the 
manure in other ways, as will be seen 
later. In using gypsum, scatter it on 
the floor immediately after the barn 
is cleaned and before the fresh bed- 
ding is spread. About one pound per 
animal each day is the amount most 
commonly used, although more will do 
no harm. It will probably pay better 
to apply all the land-plaster used on 
the farm with the manure, than to sow 
it directly on the ground. 

Kainite, muriate of potash and acid 
phosphate, or superphosphate, are of- 
ten recommended as preservatives for 
manure and to prevent the loss of ni- 
trogen. These substances are objec- 
tionable for the reason that they are 
injurious to- the hoofs of the animals. 
If used at all they should be scattered 
on the floor and carefully covered with 
bedding. Another objection to using 
superphosphate to "fix" the ammonia 
is that part of the soluble phosphoric 
acid is made insoluble by mixing it 
with manure, and as the superphos- 
phate is purchased solely for its solu- 
ble phosphoric acid, this change is un- 
desirable. Some experiments have indi- 
cated that nothing is so efficacious in 
preventing the loss of nitrogen from 
the manure as a liberal application of 
dry earth to the stable floor, especially 
if the soil used contains a large 
amount of humus. In some sections of 
the country it is considered good prac- 
tice to collect and dry out muck soil 
for use in the stable in connection with 
the bedding. There is no doubt that 
this prevents the loss of ammonia if 
properly used. Dry earth should not 
be used in large quantities, hov/ever, 
for if sufficient is added to make the 
manure very dry it will cause loss of 
nitrogen instead of preventing it. 

Mention has been made of the fact 
that manure is never so valuable as 
when perfectly fresh, for it is impos^ 
sible even under the best system of 
management, to entirely prevent loss 



of its fertilizing ingredients. For this 
reason the plan of hauling the manure 
from the barn directly to the field is 
to be recommended whenever there is 
a field available and the weather is 
suitable. This method of handling the 
manure has many points that com- 
mend it to the American farmer. In 
the first place it is the most econom- 
ical of time and labor, as the manure 
has to be handled but once, and if the 
barns are conveniently constructed, 
can be removed to the field with little 
more labor than is required to place 
it in the heap if it is stored. Where 
the manure is allowed to collect for 
long periods, it becomes alinost impos- 
sible to find the time and help neces- 
sary to haul it to the field, and the 
temptation to neglect it entirely is al- 
most irresistable. Again, almost the 
total value of the manure is realized 
when it is removed directlytothefield 
and spread over the surface of the 
ground. To be sure, the rains falling 
on this manure will leach out the solu- 
ble portion, but now it will be car- 
ried into the soil where it is needed. 
The soluble constituents of the manure 
are "fixed" by the soil so that there is 
no danger of their being lost. If the 
manure is spread in a thin layer it will 
not heat, so there will be no fear of 
hot fermentation, and it has been dem- 
onstrated that where manure simply 
dries out when spread on the ground 
there is no loss of valuable constitu- 
ents. ■ 

It is not always possible to remove 
the manure to the field immediately, 
for there may be none ready to re- 
ceive it, or the weather may be such 
as to make it undesirable to haul over 
the ground. In that case it becomes 
necessary to store the manure for a 
time, and the question is, how can this 
be done with the least loss, for it is 
impossible to entirely prevent loss in 
stored manures. 

In section 50 it was shown that the 
two sources of loss in fertilizing 
value in the manure after it is 
removed fi'om the barn are, leaching 
due to rains, and hot fermentation. 
Obviously if the maximum value of 
the manure is to be retained, these 
two injurious processes must be pre- 
vented. The effect of leaching rains 
may be overcome in two ways, by pro- 
viding water-tight receptacles so that 
the liquid cannot run away, or by keep- 
ing the manUx- ; under cover so as to 
protect it from the rains. The first of 



41 



these two methods is in general use in 
some sections of Europe. Pits or cis- 
terns of cement or other impervious 
material are built in which to store 
the manure, and in some cases a pump 
is provided so that the liquid may be 
pumped up and allowed to again run 
over the solid portion to hasten and 
control its decay. While this process 
results in the production of manure of 
excellent quality, it has little to rec- 
ommend it to the American farmer, 
for it requires too much time and labor 
to prepare it, and is not easy to apply 
to the field. Protection of the manure 
from leaching rains by keeping it un- 
der cover is more practical and should 
be in general use, for an inexpensive 
shed or lean-to is all that is required. 
Where it is possible to provide the 
shed with a floor of some water-tight 
material it is of course desirable to 
do so, as that prevents danger of loss 
of any liquid excrement that might 
not be properly absorbed by the bed- 
ding. 

The whole secret of preventing hot 
fermentation may be summed up in 
these few worus: "Keep the manure 
heap compact and moist." It has been 
shown that lue heating of manure is 
caused by a class of bacteria which 
require free oxygen for the perform- 
ance of their functions. Unless these 
bacteria are provided with sufficient 
air it is impossible for them to live, 
and consequently hot fermentation 
cannot occur. In building the manure 
pile, therefore, great care should be 
taken to have the heap well compacted 
by tramping or other means. Each 
daily addition to the pile should be 
firmly packed into place and the sides 
and top of the heap should be smooth 
and firm in order to exclude as much 
air as possible. If the pile is made 
in this way the aerobic bacteria soon 
use all the air that is enclosed in it, 
and the manure never becomes very 
hot. The presence of an abundance 
of moisture tends to prevent hot fer- 
mentation, due first to the cooling 
effect of the moisture itself, and to the 
fact that the moisture prevents the 
entrance of air. The manure heap 
should be carefully watched and water 
added to it occasionally if it shows 
any tendency to become too dry. Keep- 
ing the pile compact and damp in this 
way will stop the injurious hot fer- 
mentation, but does not interfere with 
the decay due to anaerobic bacteria. 
The latter is beneficial because it de- 



composes the organic matter of the 
manure in such a way that the plant 
food becomes more available, and the 
manure is greauy improved in its me- 
chanical condition. The first step in 
the preservation of manure should be 
the mixing of the different kinds pro- 
duced on the farm, for in this way the 
rapid fermentation that would take 
place in the dryer horse and sheep 
manure is checked by the more moist 
cow and pig excrement. When it is 
possible to do so, turn the manure oc- 
casionally, for this will cause it to de- 
compose more readily and evenly. 
When it is necessary to store the ma- 
nure for some time it is a good plan 
to cover the heap with an inch or two 
of earth. This prevents the escape 
of any ammonia that may be formed, 
as the earth has the power of fixing 
and retaining the ammonia. 

Roberts and other writers recom- 
mend the use of covered barnyards 
for the preservation of manure. These 
are simply sheds with good roofs but 
no sides, and large enough to allow the 
cattle some room to move about. The 
bottom is excavated a few inches and 
made tight by puddling and pounding 
the clay or by use of grout. The ma- 
nure as it is removed from the barn 
is spread evenly on the floor of the 
covered yard, is tramped into a com- 
pact mass by the cattle and is kept 
moist by the liquid excrement. The 
manure produced in this way is of ex- 
cellent quality, can be easily handled 
when its removal is necessary and ex- 
periments indicate that the losses are 
reduced to a minimum. The advan- 
tages of such a covered yard as a place 
in which the cattle may take mild 
exercise in severe weather will be ap- 
parent to most farmers. 

A method of preserving manure that 
is in use in some parts of Europe is 
what is known as the "deep stall 
method." The stalls in which the cat- 
tle stand are excavated for some depth 
below the general level of the barn 
floor, and every day the manure is 
spread evenly over the stall and a lib- 
eral amount of bedding added. The 
mixture of excrement and bedding is 
firmly packed by the feet of the cat- 
tle and is not removed until the end 
of the winter, the surface of the ma- 
nure being by this time above the 
level of the floor. The manure pro- 
duced in this way is of excellent qual- 
ity and suffers very little loss in fer- 
tilizing value. This method will hardly 



42 



commend itself to the farmers of this 
country for sanitary reasons, especially 
if they are engaged in dairy hus- 
bandry. 

The plan followed by many agricul- 
turalists of throwing horse and cattle 
manure into a basement room and 
allowing it to be worked over by the 
hogs is perhaps as good a method as 
could be devised when considered 
from the preservation of manure stand- 
point. The working over and tramp- 
ing of the manure by the swine accom- 
panied by the addition of their own 
moist excrement, controls the fermen- 
tation so as to prevent undue heating, 
and very little fertilizing value is lost 
from manure produced in this way if 
the number of pigs is suflBcient to 
thoroughly work it over. 

Occasionally it becomes absolutely 
necessary to store the manure when 
no cover of any kind is at hand. In 
case it must be left in the open the 
heap should be made so high that even 
the hardest rains will not soak en- 
tirely through it. The sides of the 
pile should be kept as nearly perpen- 
dicular as possible, and the top should 
dip slightly toward the center, and 
great care be exercised to make the 
heap compact. 

(52) Composting Manures. — Any 

method of storing manure requires 
considerable labor, and for that reason 
is to be avoided in general farming 
whenever it is possible to use it in the 
fresh condition. In market gardening, 
on the other hand, such quantities of 
manure are used that it is necessary 
to have it thoroughly rotted before 
applying, as otherwise the crop would 
suffer from the heating effect that the 
large amount of raw manure would 
have on the soil. While the manure 
may be rotted by keeping it in a moist 
compact heap as described in the pre- 
vious section, it must be remembered 
that the manure commonly used by 
market gardeners is the horse manure 
from the city stables. This heats so 
rapidly that special care is necessary 
to prevent hot fermentation, and the 
pile must be frequently moistened. 
Many market gardeners prefer to com- 
post the manure with earth or muck. 
This is done by making a foundation 
of about six inches of dirt and on top 
of this placing alternate layers of soil 
and manure, moistening the mass as 
the heap grows. The sides and top 
should be nicely smoothed off and the 



mass covered with a thin layer of 
earth to prevent loss of nitrogen. 
After about two months the pile should 
be turned over, the materials thor- 
oughly mixed and more water added 
if necessary to keep the compost 
moist. 

A compost in great favor with green- 
house men is one made of manure and 
sod, these materials being piled in al- 
ternate layers as described above. 
This gives the fibrous compost so de- 
sirable for bench and pot work. Any 
of the refuse organic materials otf 
the farm or garden may be used in 
composts. Weeds, refuse parts of 
plants, dead animals, kitchen wastes, 
etc., may be added to the manure- 
earth mixture, or composted separ- 
ately, for handled in this way they de- 
compose rapidly and without offensive 
odors. The presence of the earth de- 
creases the loss of ammonia where 
highly nitrogenous materials are used. 

Some market gardeners throw the 
horse manure as it comes from the 
city stables into the pig pens to be 
first worked over by the pigs and then 
composted with the earth, and this 
plan is no doubt a wise one. 

In using composts a good practice 
is to add bone meal and one of the 
potash salts to the heap. In this way 
the plant food in the bone meal is 
made more available to the plants and 
the compost is made more valuable. 

It occasionally happens that one 
wishes to produce a stock of well-rot- 
ted manure in a very short time. This 
can be done by mixing the manure 
with a small quantity of freshly 
slaked lime. In this way the manure 
is made to decay very rapidly, but as 
the decomposition is probably attend- 
ed by more loss of nitrogen than usu- 
ally occurs in composts, it is not to 
be recommended for general use. 

(53) Applying iVlanure. — Nature ap- 
plies all her fertilizers to the surface 
of the ground. Many farmers have 
come to the conclusion that Nature's 
method is the best, and whenever pos- 
sible are using manure as a top dress- 
ing. The tendency is for the elements 
of fertility to gradually pass down in 
the soil, especially the compounds con- 
taining nitrogen. For this reason it is 
best to apply the fertilizer to the sur- 
face so that the soluble food as it de- 
scends comes in contact with plant 
roots, and is not carried to such a 
depth as to be beyond their reach. Ma- 



43 



nure to be used in this way must be so 
fine as not to interfere seriously with 
the subsequent tillage of the ground. 
This condition of fineness generally 
exists if the manure is well rotted, 
but even fresh manure may be utilized 
as a top dressing if cut straw, or 
other fine material, has been used for 
bedding. It is well to apply the ma- 
nure directly after plowing, and to 
thoroughly incorporate it with the soil, 
by use of the harrow or cultivator, pre- 
paratory to planting the field. 

Two general methods for the appli- 
cation of manure are in common use; 
one is to throw it into heaps where it 
is allowed to remain some time before 
being spread; the other to broadcast it 
directly from the wagon. The first 
method is objectionable for several 
reasons. In the first place it increases 
the work necessary to spread the ma- 
nure, as it must be twice handled, and 
it takes no more labor to spread it 
from the wagon than from the heap 
on the ground. When piled in this 
way the manure is very often allowed 
to stand for some days at great risk 
of injurious fermentations such as de- 
scribed in (50). The leachings from 
these heaps make the spots directly 
beneath them more fertile than the 
rest of the field and, hence, produce a 
rank growth at those places. No 
doubt the reader has often seen a 
field where he could detect every spot 
on which the manure heap had been 
placed by the greener and more lux- 
uriant growth of the crop. This un- 
even growth is undesirable, because in 
the case of grains it increases the 
danger of lodging in the more fertile 
spots, and in any case It results in 
unevenness in the maturity of the 
crop. A crop that has a large supply 
of plant food for instance, has a 
longer period of growth than one with 
a meager supply, and consequently is 
later in maturing. If, therefore, the 
field is very uneven in fertility a part 
of the crop will be ready to harvest 
some time before the rest has ma- 
tured. If the manure is spread di- 
rectly from the wagon not only is the 
labor lessened but the danger of un- 
evenness in growth is to some extent 
avoided. There is no likelihood of loss 
in the value of the manure when it is 
spread in a thin layer on the ground 
as has already been stated, (51). Ma- 
nure spreaders are now being offered 
for sale of such efl3.ciency that they 



are likely to come into general use. 
Whatever method is used to spread 
the manure it will readily be seen that 
the finer the material the easier it 
will be to distribute it evenly. Where 
very coarse manure is used some farm- 
ers find it advantageous to supplement 
the spreading from the wagon by the 
use of a drag that will break up the 
larger lumps and distribute it more 
evenly. A reason in favor of top 
dressing over other methods of ap- 
plying manure is, that the organic 
matter added to the surface soil in 
this way acts as a mulch, and tends to 
prevent the evaporation of water from 
the soil. 

Where the manure is so coarse as 
to interfere with tillage it becomes 
necessary to plow it under, and in this 
case some discretion should be used to 
prevent its being covered to too great 
a depth. Especially in clay soils, 
where the air does not readily enter, 
it is easily possible to bury the ma- 
nure so deeply as to prevent decay. 
In the case of heavy soils the manure 
should probably never be covered to 
a greater depth than four inches, while 
in sandy soils the depth might be much 
greater. In very dry seasons much 
harm may be done to the soil by 
plowing under large quantities of 
coarse manure, as there may not be 
sufficient moisture in the soil to bring 
about the decomposition of the organic 
matter, and the undecayed material 
may cause serious injury to the phys- 
ical condition of the soil as was noted 
in the discussion of green manures 
(38). A practice that is highly recom- 
mended is to apply the manure, espe- 
cially that of the summer and early 
fall, to sod land that is to be plowed 
and planted the following spring. In 
this way of utilizing manure the 
soluble part, as it is washed out by the 
rains, is used by the growing crop, 
and thus the losses due to leaching 
are avoided an<3, as the stubble or sod 
is turned under, the entire amount of 
plant food is in position to be used 
by the succeeding crop. The 
permanent pastures should not be ne- 
glected in manuring and will well re- 
pay liberal applications. It is well to 
use the drag mentioned above on the 
pastures, so as to spread the drop- 
pings of the cattle evenly over the 
surface. 

Few questions have been more dis- 
cussed by the agricultural press than 



44 



the relative merits of fresli and rotted 
manures, and the apparently incon- 
sistent results reported by different 
farmers are probably due more to 
various kinds of soil on which the 
manure was used, than to any differ- 
ence in the values of the manures 
themselves. Considered from the 
standpoint of the soil alone it will be 
found that on heavy soils containing 
large amounts of clay more benefit 
will be derived from raw manures 
than from those that are well rotted. 
The fresh manure warms these natu- 
rally cold soils, makes them more 
porous, and the fermentations that 
take place during its decay tend to 
make the soil more mellow, and to set 
free the "locked up" plant food. 
Rotted manure has the same effect 
but in a less marked degree than that 
which is fresh. On light or sandy 
lands on the other hand those manures 
that are well decomposed will be 
found more beneficial. Such soils are 
likely to suffer from the heating and 
drying effect of raw manure, and to 
have their porosity increased to an 
undesirable extent. The manure used 
on these soils should be thoroughly 
decayed, and will thus be found to im- 
prove the mechanical condition of the 
soil, and to materially increase its 
moisture retaining power. 

Raw manures induce rank growth 
and for that reason are objectionable 
for use on the small grains, where 
the product desired is the grain, and 
not the yield of leaf and stem. If ma- 
nure is used directly on these crops it 
should be thoroughly decomposed. 
Corn, millet and the hay crops, on the 
other hand, are usually benefitted by 
liberal applications of fresh manure. 
Corn especially is a gross feeder, and 
apparently is not injured by the 
heaviest application of raw manure, in 
fact, it may be said that when the 
farmer is in doubt as to where to ap- 
ply the manure he should use it on the 
corn. Manures that are at all fresh 
are injurious to sugar beets and to- 
bacco, in the former case producing a 
large beet that is low in sugar con- 
tent, and in the latter a coarse and un- 
desirable leaf. It is also a well-known 
fact that raw manure is likely to make 
wheat lodge. 

Instead of using manure directly on 
the grain, beets or tobacco it is cus- 
tomary, in some parts of the coun- 
try, to apply it liberally to corn, and 



plant the field to the above mentioned 
crops the following year. Using it 
this way there is no danger of induc- 
ing rank growth. 

In a few instances manures are 
wasted by being used too liberally. 
For ordinary farm crops it probably is 
never profitable to use more than ten 
to fourteen tons per acre, and on gen- 
eral principles it may be stated that 
somewhat frequent light applications 
will pay better than very large ones 
given at long intervals. On the other 
hand the amount of manure produced 
on the average farm is so small, when 
compared with the land to be ferti- 
lized, that it would be utterly impos- 
sible to spread it over all the farm 
each year; for this reason, it is a good 
plan to apply the manure to one crop 
in a rotation, thus covering only a 
fraction of the farm each year. The 
following rotation which is used by a 
well known dairyman is an example 
that will explain the last statement; 
corn 1 year, grain 1 year, clover and 
timothy 2 or 3 years. The manure is 
applied the last year the field is in sod. 
A second rotation in common use is 
as follows: corn (manured), grain, 
clover, grain. Chemical fertilizers as 
well are often used on one or both 
grain crops. 

(54) Usefulness of Manure. — 

Some difference of opinion exists 
among farmers as to the relative value 
of barnyard manure and commercial 
fertilizers for crop production, but it 
is worthy of note that those who are 
most diligent in caring for the manure 
are the ones who have most faith in 
its worth as a fertilizer. The fact 
that barnyard manure has been used 
so universally by agriculturalists, and 
for so many centuries is one of the 
strongest arguments in its favor. 
That the popular estimate of its 
value is established by scientific ex- 
periment is well shown by investiga- 
tions carried on at Rothamsted. On 
certain plots, as has been mentioned, 
crops have been grown continuously 
with no fertilizer of any kind added; 
on other plots barnyard manure has 
been used every year, and on still 
others various combinations of com- 
mercial fertilizers have been tested. 
The following table gives the yields of 
barley and wheat from the unmanured 
plots, the plots dressed with barnyard 
manure, and the highest results ob- 
tained from the use of any combina- 



45 



tion of commercial fertilizing mate- 
rials. The tests extend over forty 
years, but to shorten the table the re- 
sults are given here in averages for 
five eight-year periods. (Fractions 
have been omitted). 



vious twenty years. The figures given 
for the second plot represent the 
effect of the residual manure as no 
fertilizer was added during the period 
covered by the table. 





BARLEY 1 


WHEAT 




Bushels per 


Acre 


Bushels per Acre 




u 






aj 










■^ .^ 








■ - rTi 








'J - 










n 


re b 


ej K 


?. 




flj -ri 




S 


•~ « 


^ w 


% 


E rt 


C.™ 




o 


r:^ 




o 


^C^ 


S t! 




Z 


^ 


Ufe 


Z 




Ofa 


1st 8yrs. 


24 


44 


48 


16 


34 


36 


2nd 8 " 


18 


52 


51 


13 


35 


39 


3rd 8 " 


14 


49 


45 


12 


35 


36 


4th 8 " 


14 


52 


42 


10 


28 


32 


Sth 8 " 


11 


44 


41 


12 


39 


38 


Average 


16 


48 


45 


13 


34 


36 


(40yrs.) 















It will be seen that while both the 
fertilized plots gave much larger 
yields than the one receiving no ad- 
dition of plant food, there is practi- 
cally no difference between the plots 
dressed with barnyard manure and the 
best commercial fertilizers. This test 
is hardly fair to the barnyard manure, 
as the quantities of commercial ferti- 
lizers applied were far in excess of 
anything used in general practice; the 
amount of nitrogen added to the 
wheat, for instance, being equivalent 
to that contained in 800 pounds of 
nitrate of soda, which would cost prac- 
tically as much as the wheat would 
bring on the market. In all proba- 
bility, if these experiments had been 
conducted in this country the showing 
would have been much more favorable 
to barnyard manure. It has been ex- 
plained that the materials in the ma- 
nure must undergo nitrification be- 
fore the nitrogen becomes available 
to plants, and this process takes place 
so much more rapidly in this coun- 
try than in England, that it is easy 
to believe better returns might be ob- 
tained from barnyard manure under 
American conditions. 

Barnyard manure differs from other 
fertilizers in its lasting effect when ap- 
plied to the soil. At Rothamsted in 
connection with the above experiment 
one plot was manured annually for 
twenty years, and then received no 
manure for the next twenty years. 
In the table below are given the 
yields of barley in averages for 
five-year periods on the plot 
which was never manured, and the 
plot that had been manured the pre- 





Un manured 
every year 


Effect of 
Kesidual 
Manure 




13 
14 
14 
12 


39 


Second 5 vears 

Thirds years 

Eourth 5 years 


29 
30 
23 


Average (20 yrs.). .. 


13.25 


30 



The table shows that the effect of 
the manure was perceptible in the 
yield for at least twenty years after 
the last application. It is more than 
likely that the more rapid rate of ni- 
trification in this country might ma- 
terially shorten the period in which 
the lasting effect of the manure would 
be observable, and no doubt the in- 
fluence of the residual manure would 
have disappeared in a shorter time 
than twenty years. 

The value of barnyard manure can- 
not be estimated from the content of 
nitrogen, phosphoric acid and potash 
alone. Manure is probably as valu- 
able on account of its effect on the 
mechanical condition of the soil as for 
the plant food that it contains. As 
a humus former it has no equal among 
fertilizers, and the great value of 
humus in improving the tilth of the 
soil and increasing its power to hold 
water has been shown in an earlier 
section (38). The writer believes that 
the farmer would be well repaid for 
applying the barnyard manure for its 
physical action alone, even though it 
contained none of the elements of 
plant food. 

(55). Effect of Style of Farming on 
Fertility. — The facts brought out by 
this discussion of the subject of barn- 
yard manures must have made it ap- 
parent that the losses in fertility are 
much greater in any system of farm- 
ing where the crops are sold from the 
farm, than where some form of ani- 
mal husbandry is followed, especially 
if no commercial fertilizers are used. 
To bring this point more concretely 
before the reader the following table 
adapted from a Minnesota bulletin is 
given here. In compiling the table 
it was assumed that each farm con- 
sisted of 160 acres. In the first case 
nothing but grain was raised and all 
sold from the farm, in the second the 



46 



EFFECT OF TYPES OF FARMING ON 
FERTILITY. 





GAIN OK LOSS IN FEKXrLITY 


Kind of 
Farming- 


Nitrosren 
Pounds 


Phosp'ic 

Acid 
Pounds 


Potash 
Pounds 


All Grain 

Grain and Stock 

Stock 

Dairy.. .... 


—5600 
—2600 

— 900 

— 800 


—2500 
—1000 

+ 50 
H' 75 


—4200 
—1000 

— 60 

— 85 







farm was about equally divided be- 
tween grain and stock raising, and in 
the third and fourth the farms were 
devoted to stock raising and dairying 
respectively. In the last two cases a 
small amount of potatoes and grain 



were exchanged for mill products, but 
it was assumed that no other con- 
centrates or fertilizers were used. 

Even this table does not show the 
advantages in favor of the last two 
styles of farming for, if the results 
obtained at Rothamsted from the 
growth of clover are accepted, there 
was a gain of nitrogen in the stubble 
in these two cases that would much 
more than counterbalance the losses 
shown in the table. No better illus- 
tration of the effect of the system of 
farming on the fertility of the soil 
could be desired. 



PART IV. Commercial Fertilizers. 



(56) General Considerations. — It 
was shown in Part III. that under a 
system of animal husbandry it is pos- 
sible to maintain the fertility of the 
soil by means of the barnyard ma- 
nure used in connection with legu- 
minous crops, provided the best meth- 
ods of tillage, etc. are used, and all 
the materials raised are fed on the 
farm. Where a part or all of the 
crops produced are sold from the 
farm, it sooner or later becomes nec- 
essary to supply plant food derived 
from outside sources. This is espe- 
cially true in truck farming where the 
crops raised are such as remove large 
quantities of plant food. The needed 
fertility is supplied to some extent 
by the manure produced in the city 
stables, and is best so supplied where 
possible, but this source of fertilizing 
material is obviously inadequate to 
furnish the required amount of plant 
food. 

The constantly growing demand for 
something that will increase the crop 
production has given rise to the fer- 
tilizer industry which is rapidly as- 
suming gigantic proportions. At the 
present time over fifty millions of dol- 
lars are used annually in the purchase 
of fertilizers in the United States, and 
it is probably no exaggeration to say 
that fully half of this is money thrown 
away. This is no argument against 
the use of commercial fertilizers, but 
simply means that they should be 
used with judgment and not used at 
all until actual investigation has 
shown them to be necessary. 

"One must distinguish between lack 
of plant food in the soil and other con- 



ditions which prevent good crops, for 
lack of food is not the only cause that 
makes crops suffer. In some soils 
there is insufficient porosity which 
causes the development of the roots 
to be checked. Lack of moisture, cak- 
ing of soil, retention of stagnant wa- 
ter, deficiency of humus, lime, etc., 
unfavorable weather and other condi- 
tions may interfere with the healthy 
growth of plants and thus cause di- 
minished crops, even when the plant 
has within reach all the food it needs. 
Under such circumstances the un- 
favorable conditions must be removed 
to secure good crops, which, accord- 
ing to the demands of special cases 
may be done by irrigating, draining, 
harrowing, hoeing, marling, mucking, 
etc. It may often happen that the 
soil contains an abundance of plant 
food, most of which is still unavail- 
able. Under such circumstances an 
effort should be made to bring this 
food into an available condition as 
rapidly as the plants can use it, and 
this may be done by an improved sys- 
tem of tillage, together with the ap- 
plication of such indirect fertilizers 
as have the power to make insoluble 
plant food available." (Van Slyke). 

Too frequently fertilizers are made 
to take the place of tillage when they 
should be used to supplement it. That 
is. fertilizers are most lilkely to pro- 
duce profitable results when conjoined 
with superior physical conditions of 
the soil. On general principles it may 
be said that the man who would ob- 
tain the best yield without fertilizers 
of any kind is the one most likely to 
realize a profit from their use. 



47 



"The fact that fertilizers may now 
be easily secured, and the ease of ap- 
plication, have encouraged a careless 
use, rather than a thoughtful expen- 
diture of an equivalent amount of 
energy in the proper preparation of 
the soil. Of course it does not follow 
that no returns are secured from plant 
food applied under unfavorable condi- 
tions, though full returns cannot be 
secured under such circumstances. 
Good plant food is wasted, and the 
profit possible to be derived is largely 
reduced." (Voorhees). 

(57) What are Commercial Fertiliz- 
ers? — When it was first discovered 
that certain of the elements found in 
the soil were necessary to plant 
growth, it naturally occured to the 
agricultural investigators that it 
might be possible to renew the fer- 
tility of worn out soils by supplying 
these elements artificially. In the 
first experiments conducted along this 
line all of the elements which the 
plant derives from the soil were sup- 
plied. As the investigations pro- 
gressed it was discovered that in- 
creased production resulted in most in- 
stances from the addition of only three 
of these substances, i. e., nitrogen, 
phosphoric acid and potash. In other 
words it was determined that except 
in rare cases all the other elements 
existed in the soil in quanities suffi- 
cient to supply the needs of the plant 
even when the available nitrogen, 
phosporic acid and potash were prac- 
tically exhausted. For this reason it 
is generally considered unnecessary 
to supply any of the elements of plant 
food except the three named above, 
and these substances have come to be 
known as the "essential ingredients of 
a fertilizer," and the only ones that 
give the fertilizer a commercial value. 

Prom what has been said it will be 
seen that any material that supplies 
one or more of these "essential in- 
gredients" might be used as a com- 
mercial fertilizer provided it could 
be purchased at a price that would 
make its use profitable. As a matter 
of fact the number of substances that 
are available for this purpose is some- 
what limited, owing to the prohibitive 
prices which the others bring on the 
market. 

Many persons seem to think that 
there is something mysterious about 
the manufacture of fertilizers, and 
some of the makers encourage this 



belief by pretending that they have 
some secret process of manufacture, 
that enables them to produce a better 
product than their competitors, and 
far better than the farmer can mix 
himself. The truth is that there are a 
limited number of basic materials 
from which all the different brands of 
fertilizers are made and these basic 
substances are articles of commerce 
and can be purchased by anyone. The 
so called "complete fertilizers" consist 
of two or more of these substances 
mixed together, in the proportion to 
give the required per cent of nitrogen, 
phosphoric acid and potash in the fin- 
ished product. Some of these ma- 
terials are commonly purchased un- 
mixed, while others are rarely seen 
by the farmer except as one of the 
ingredients of a complete fertilizer. 
Some of these basic materials contain 
only one of the essential ingredients 
of a fertilizer, while others contain 
two, but usually one is in such excess 
that the substance is used chiefly to 
furnish that one element. It is pos- 
sible, therefore, to separate the basic 
fertilizers into three classes; viz: 

(1) Materials used chiefly as 
sources of nitrogen. 

(2) Materials used chiefly as 
sources of phosphoric acid. 

(3) Materials used chiefly as 
sources of potash. 

In order to discuss intelligently the 
subject of commercial fertilizers it will 
be necessary to briefly consider the 
substances included in these different 
classes. 

(58) Nitrogenous Fertilizers. — The 
larger number of this class are com- 
posed of various kinds of refuse ani- 
mal matter fram the packing houses, 
soap and glue factories, etc. Only 
those in common use will be discussed 
here. 

DRIED BLOOD. As its name signi- 
fies this is the blood from the slaugh- 
ter house which has been rapidly 
dried by artificial heat, and when 
ready for sale is in the form of a pow- 
der. Two grades of dried blood are 
found on the market, known as the 
red and black blood. The red blood 
is more carefully dried and is not 
charred as is likely to occur with the 
more rapid drying that produces the 
black blood. The red blood contains 
from 13 to 14 per cent of nitrogen. 



48 



while the black is much less constant 
in composition, and contains from 6 to 

12 per cent. 

MEAT MEAL, AZOTIN, AMMO- 
NITE. These are synonomous terms 
used to designate a meat product de- 
rived principally from the rendering 
establishments, where the different 
portions of dead animals are utilized. 
When relatively pure it contains from 

13 to 14 per cent of nitrogen. 

HOOF MEAL. The principal source 
of this product is the glue factory, 
and consists of the dried hoof or por- 
tions thereof ground to a fine powder. 
It is fairly uniform in composition 
and contains about 12 per cent of 
nitrogen. 

HORN MEAL is produced at the 
packing houses and in the factories 
where combs, buttons, etc., are manu- 
factured. The chips and shavings are 
ground to a fine meal and sold as a 
fertilizer. It is quite uniform in com- 
position, containing from 10 to 12 per 
cent of nitrogen — though in a very 
unavailable form. 

TANKAGE consists of the dried 
animal wastes from the large slaugh- 
tering establishments. It is variable 
in composition owing to the fact that 
the proportions of the different in- 
gredients of which it is composed 
may vary widely in different samples. 
As commonly made it may include 
offal, small bones, tendons, waste 
flesh, hair, etc. These materials are 
rendered for the extraction of the fat, 
and the residue is dried and ground 
to a meal of more or less fineness. 
Tankage contains phosphoric acid as 
well as nitrogen, and the percentage 
of the two vary. As the nitrogen de- 
creases the phosphoric acid increases 
and vice versa. The variation of 
these two ingredients is so great that 
in trade it is always sold on the basis 
of its composition. Because it con- 
tains very considerable amounts of 
phosphoric acid its commercial value 
is not based wholly on its nitrogen 
content as is the case with dried blood 
and dried meat. Tankage contains 
from 4 to 9 per cent of nitrogen and 
from 3 to 12 per cent of phosphoric 
acid. 

DRIED FISH OR FISH GUANO. 
Most of the fish fertilizers are made 
from the menhaden, a fish that is 
caught in large numbers along the 



Atlantic coast. The fish are steamed 
and pressed to extract the oil and the 
remaining "pomace" is dried and 
ground. This material contains from 
8 to 11 per cent of nitrogen and 3 to 5 
per cent of phosphoric acid. Some of 
the fish fertilizers consist of the resi- 
dues of the canning factories, but 
those are not so valuable as those 
derived from the menhaden. 

LEATHER MEAL consists of the 
smaller scraps and chips from the 
leather industry that are collected and 
ground into a meal which is some- 
times used in the manufacture of fer- 
tilizers. Leather is fairly rich in ni- 
trogen but, taking into consideration 
that the one object in making leather 
is to render it resistant to the condi- 
tions which promote decay, it will be 
seen that is not a desirable substance 
to use as a fertilizer. 

COTTONSEED MEAL AND LIN- 
SEED MEAL were formerly used as 
nitrogenous manures, but their value 
as feeds is now so well recognized 
that they are no longer available as 
fertilizers. 

PERUVIAN AND OTHER GU- 
ANOS. These are composed of the 
accumulated droppings of fish eating 
birds, more or less mixed with the 
dead bodies of these birds. The most 
important source of this material was 
a group of islands lying off the coast 
of Peru, and its high value was due to 
its being produced in a rainless re- 
gion. Guano was formerly abundant, 
and was so much appreciated as a 
fertilizer that many substances in no 
way resembling the true guanos were 
called by that name. At the present 
time practically no guano of good 
quality is imported and any product 
bearing that name should be looked 
upon with suspicion and purchased 
only upon analysis. 

SULPHATE OF AMMONIA, is a by- 
product of the manufacture of coal 
gas, animal charcoal and coke. It 
resembles common salt somewhat in 
appearance and is the richest in nitro- 
gen of all fertilizing materials, con- 
taining from 20 to 23 per cent. At the 
present time the high price of the 
sulphate interferes with its extensive 
use, although it gives excellent re- 
sults on soils that contain plenty of 
lime. It should never be used on 
soils deficient in lime nor in con- 



49 



nection with the ordinary potash fer- 
tilizers which contain chlorine. 

NITRATE OF SODA OR CHILI 
SALTPETER. This is a crystalline 
substance, somewhat resembling 
coarse salt in appearance, and is en- 
tirely soluble in water. It all comes 
from large deposits in Chili, which 
supply over one million tons of nitrate 
per year to be used as a fertilizer. 
Chili saltpeter contains from 15 to 16 
per cent of nitrogen in a form that is 
immediately available to the plant, 
and for this reason it is the most de- 
sirable nitrogenous fertilizer to use 
where immediate results are desired. 
It is not fixed by the soil and conse- 
quently should be supplied only as the 
crop can use it, and never applied to 
the ground when it is bare. As it is 
so easily washed from the soil it is 
considered best to use it in two or 
three applications instead of applying 
all at one time. 

(59) Relative Availability of Nitro- 
genous Fertilizers. — The per cent of 
nitrogen present in the different fer- 
tilizing materials, as given in the pre- 
vious section, does not properly indi- 
cate their relative fertilizing value. 
Mention has repeatedly been made of 
the fact that the plant can make use 
of the nitrogen only when it is present 
in the soil in the form of nitrates. Ni- 
trate of soda is the only fertilizer on 
the list that contains nitrogen in the 
nitrate condition, and consequently is 
the only one that adds nitrogen to 
the soil in a form that is available to 
the plant without further change. All 
the other materials must undergo the 
process of nitrification and have their 
nitrogen converted into nitrates be- 
fore it can be used by the crop. It 
jmust be apparent, then, that the value 
of a nitrogenous fertilizer depends 
upon both its content of nitrogen and 
the ease with which it is nitrified. 

Of the list given above sulphate of 
ammonia is the most easily converted 
into nitrates, provided the soil is 
abundantly supplied with lime. Next 
in order comes dried blood. So many 
other uses are being discovered for 
dried blood, however, that the time is 
probably not far distant when it can 
no longer be used as a fertilizer. 

The nitrogen in dried fish, tankage, 
hoof meal and bone meal are readily 
changed by nitrification and rank 



next to blood meal. Horn meal on 
the other hand decomposes very 
slowly, and the nitrification of leather 
is so slow as to make it practically 
worthless as a fertilizer. 

Experiments up to date indicate 
that if nitrate of soda is rated at a 
100 per cent the availability of the 
other materials would be as follows: 

Nitrate of soda 100 

Blood and cottonseed meal 70 

Fish, hoof meal 65 

Bone and tankage 60 

Leather and wool waste. . .2 to 30 

"If, for example, the increased yield 
of oats due to the application of ni- 
trate of soda is 1,000 pounds, the 
yield from blood would be 700 pounds, 
from hoof meal 650 pounds and leather 
20 to 200 pounds." 

These statements indicate how little 
an analysis of a fertilizer which gives 
only the per cent of nitrogen or am- 
monia tells of the real value as a sup- 
plier of nitrogen, and show very 
clearly that to arrive at any conclu- 
sion regarding the value of a nitro- 
genous fertilizer one should know the 
source or condition of the nitrogen 
as well as the per cent. 

Two or three suggestions for the 
selection of nitrogen fertilizers may 
be deduced from this discussion. For 
those crops which begin their growth 
early in the spring the best results 
will follow the use of Chili Saltpeter, 
as the soil is likely to be poor in ni- 
trates and the process of nitrification 
is slow at that time. Such crops as 
have very short periods of growth 
will respond best to nitrogen in ni- 
trates. Corn, on the other hand, and 
the other crops which make their 
growth after the season is well ad- 
vanced can use the slower acting fer- 
tilizers, as can also those crops which 
occupy the ground permanently. Some 
agriculturists prefer to use a fer- 
tilizer containing nitrogen in three 
forms for the crops that grow during 
the greater part of the season ; a little 
nitrate of soda for immediate use, 
sulphate of ammonia to supply nitro- 
gen a little later, and tankage to carry 
the plant to maturity, all these ma- 
terials being mixed and applied at 
one time.. 



SO 



(60) Potash Fertilizers. — It has 
been shown that most soils contain 
much more potash than nitrogen or 
phosphoric acid. (28.) The greater 
part of the potash in the soil is in very 
insoluble and unavailable forms, and 
although there are large quantities 
present, the plant may be able to use 
so little of it that a good crop is im- 
possible, as has been shown by the in- 
creased yield from the use of potash 
on clay soils that had a high content 
of this element of fertility. 

"It has been attested that potash is 
of relatively less importance than 
either nitrogen or phosphoric acid, 
inasmuch as good soils are naturally 
richer in this element, and because a 
less amount is removed in general 
farming than of either nitrogen or 
phosphoric acid, as the potash is lo- 
cated to a less extent in the grain 
than in the straw, which is retained 
on the farm. It is, however, a very 
necessary constituent of fertilizers, 
being absolutely essential for those 
intended for light, sandy soils and for 
peaty meadow lands, as well as for 
certain potash-consuming crops, as 
potatoes, tobacco and roots, since 
these soils are very deficient in this 
element, and the plants mentioned re- 
quire it in larger proportion than do 
others. In fact, it is believed by many 
careful observers, — and the belief has 
been substantiated in large part by 
experiments already conducted, — that 
the average commercial fertilizer does 
not contain a sufficient amount of this 
element. It is a particularly useful 
element in the building up of worn-out 
soils, because contributing materially 
to the growth of the nitrogen-gather- 
ing legumes, an important crop for 
this particular purpose." (Voorhess.) 

The statement so often made by 
fertilizer manufacturers that potash is 
not necessary in a commercial ferti- 
lizer, because it is present in such 
quantities in the soil, does not take 
into consideration the fact that it is 
only the available plant food that is 
of importance to the present crop, 
and that the larger part of the food 
in the soil may be in unavailable or 
potential forms. 

WOOD ASHES at one time was the 
sole source of potash for fertilizing 
purposes, but at present ashes supply 
but a very small proportion of this ele- 
ment of plant food. The potash in 
wood ashes is in one of the best forms 
for use as a fertilizer, but the supply 



is so limited and the price usually de- 
manded so high that ashes can no 
longer be considered an important 
source of potash. Wood ashes vary 
greatly in composition, and ash from 
soft wood containing less potash than 
that from the bar woods; the content 
of potash ranging from 2 to 8 per cent. 

Potash as found in wood ashes is 
in a form that is very soluble in water 
so that ashes that are exposed to the 
weather may have practically all of 
the potash leached out of them; 
leached ashes as a rule contain less 
than 2 per cent of potash. As it is 
not possible to distinguish between 
leached and unleached ashes by mere 
physical examination, it is evident 
that this material should be purchased 
only from guaranteed analysis. 

In addition to potash ashes contain 
from 25 to 30 per cent of lime and in 
many cases, no doubt, the beneficial 
results obtained from ashes were due 
as much to the lime in them as to 
the potash. All ashes produced on the 
farm should be carefully preserved 
and utilized, but they can seldom be 
purchased to advantage. 

STASSFURT SALTS. At the pres- 
ent time practically all of the potash 
used in fertilizers comes from the 
Stassfurt Mines in Germany. These 
mines contain immense deposits of 
potash and are owned by a syndicate 
that controls the price and output of 
potash the world over. A number of 
different minerals containing varying 
per cents of potash are produced from 
the mines, and many of them are used 
in Germany. Only three or four of 
these products are in use in this coun- 
try, and these are the only ones that 
will be discussed here. 

KAINIT. This is one of the crude 
salts which has been ground to a pow- 
der. It looks somewhat like common 
salt but is darker in color and con- 
tains about 12.5 per cent of potash, in 
the form of sulphate, mixed with the 
sulphate and chloride of magnesia. 
This substance has been used because 
it is chaper per ton than the next two 
substances to be mentioned, but even 
at the lower price per ton, the actual 
potash costs more in kainite than in 
the concentrated salts. 

MURIATE OF POTASH is manu- 
factured from the crude minerals of 
the mines by concentration, and con- 
tains about 50 per cent of potash, all 
of which is combined with chlorine in 



51 



the form known by the chemists as 
potassium chloride. At the present 
price per ton, the muriate supplies 
potash at a cheaper price per pound 
than any of the other materials. 

SULPHATE OF POTASH is an- 
other concentrated product of the 
Stassfurt industry. What is known as 
high grade sulphate contains about 53 
per cent of potash in the form of 
sulphate (i. e. combined with sulphuric 
acid). The actual potash in this com- 
pound costs a trifle more per pound 
than in the muriate. A lower grade 
sulphate, containing about 26 per cent 
of potash, mixed with sulphate of 
magnesia, is sold under the name of 
"double manure salt." Although the 
price per ton of this material is much 
less than the muriate or high grade 
sulphate, the cost of the actual potash 
is a little more. 

(61) Comparison of Potash Ferti- 
lizers. — All of the materials mentioned 
contain potash in forms that are 
soluble in water so that there is no 
such marked difference in availability 
as was noted in the case of the nitro- 
gen fertilizers, but there is a differ- 
ence in their effect on certain crops 
and soils, due to the substances with 
which the potash is combined. The 
form in which th epotash occurs in 
wood ashes is probably the best of all, 
especially for use on light soils and 
those which are rich in humus or are 
inclined to be sour; but at the prices 
demanaed for wood ashes at the pres- 
ent time the potash costs more per 
pound than in any of the German 
salts. 

The chlorine in the muriate has 
been found to be injurious to certain 
crops, among which may be mentioned 
potatoes, tobacco and sugar beets. 
Nearly all crops are harmed by the 
muriate if it is applied in large quan- 
tities immediately before or after seed- 
ing. This injury may be prevented by 
sowing the muriate in the fall, as the 
potash will become fixed by the soil 
and the chlorine will be leached out. 
When the chlorine is removed in the 
soil water it carries with it part of the 
lime, so that the soil in fields which 
are continuously manured with muri- 
ate may become sour through removal 
of the lime. This may be prevented, 
of course, by occasional applications of 
lime. The same remarks apply to 
the use of kainite. As the muriate is 
the cheapest form of potash it is the 
compound that is used nearly alto- 



gether in mixed commercial fertilizers. 
So far as has been determined 
no injurious effect results from the 
use of sulphate of potash, and some 
experiments indicate that larger yields 
per pound of potash are obtained from 
the sulphate than from any of the 
other salts. It is the only potash salt 
that can be safely used on pototoes, 
sugar beets or tobacco. Although the 
potash in the sulphate costs a trifle 
more per pound it probably will not 
prove the dearer in the long run, if 
the necessity for liming where the 
muriate is used is taken into consider- 
ation; so that for continued use the 
sulphate is undoubtedly to be pre- 
ferred. 

(62) Phosphatic Fertilizers. — Phos- 
phoric acid is present in the soil in 
much smaller quantities than potash, 
and experience shows that it is much, 
more likely to become exhausted. In. 
fact there are sections of the country 
where no other fertilizers than those 
furnishing phosphoric acid are used, 
while these are bought in large quan- 
tities. All this class of fertilizers 
contain their phosphoric acid in the 
form of phosphates i. e., the phos- 
phoric acid is combined with some 
basic substance which is generally 
lime. The phosphates may be subdi- 
vided into two general classes — the 
"natural" and the "manufactured phos- 
phates." 

(63) Natural Phosphates. — There 
are two general sources of phos- 
phates — the bones of dead animals 
and certain phosphate, containing 
minerals which will be briefly con- 
sidered. 

RAW BONE MEAL is made by 
grinding raw bones into a powder, and 
the finer it is the more valuable the 
product. This substance contains 
about 22 per cent of phosphoric acid 
and 4 per cent of nitrogen. Raw bones 
contain a small quantity of fat as well, 
and as this prevents the rapid decay 
of the bone the phosphoric acid and 
nitrogen in it are somewhat slowly 
available to the crop. 

STEAMED BONE MEAL. Most of 
the bone meal sold at the present time 
is made from bones that have been 
previously steamed to remove the fat 
and a part of the nitrogen compounds. 
The fat is used in making soap, and 
the nitrogen in glue and gelatins, 
bteamed bone contains from 28 to 30 
per cent of phosphoric acid and about 



52 



one and one-half per cent of nitrogen. 
The steamed bone can be ground to a 
much finer powder, and the removal 
of the fat causes them to decay more 
rapidly so that they must be consid- 
ered a more valuable source of phos- 
phoric acid than the raw bones. 

TANKAGE was considered under 
nitrogenous fertilizers, and is an im- 
portant source of phosphoric acid in 
the so called "animal fertilizers." 
When the product contains a very 
large proportion of bone it is some- 
times designated as "bone tankage," 
and may contain from 17 to 18 per 
cent of phosphoric acid. 

BONE BLACK OR ANIMAL CHAR- 
COAL is made uy heating bone in air- 
tight vessels until all volatile matter 
is driven off, and is used in the refiner- 
ies to purify sugar. After it has be- 
come "spent" or useless to the refiner 
it is sold for use as a fertilizer. Bone 
black contains from 32 to 36 per cent 
of phosphoric acid. 

MINERAL PHOSPHATES. In a 
number of places rock deposits are 
found that contain varying percent- 
ages of phosphate of lime. These phos- 
phates are usually named after the 
place where they are obtained, as 
"Carolina phosphates," "Florida phos- 
phates," and "Tennessee phosphates." 
These rocks contain from 18 to 32 per 
cent of phosphoric acid and differ 
from the bone products in that they 
are purely mineral substances and 
contain no organic matter. Ground 
into a fine powder they are sometimes 
sold under the name of "floats," but 
the rock phosphates are used only to 
a limited extent in the crude condi- 
tion. 

(64) Superphosphates or Manufac- 
tured Phosphates. — The phosphoric 
acid in all of the natural phosphates 
described is combined with lime in a 
form that is extremely insoluble in 
water. In order to make the phos- 
phate soluble it is sometimes treated 
with sulphuric acid, which unites with 
part of the lime, leaving a phosphate 
which contains only one-third as much 
lime as the natural phosphate and 
which is soluble in cwater. The lime 
and sulphuric acid make a compound 
which is the same as that found in 
gypsum or land plaster. This combi- 
nation of soluble phosphate and gyp- 
sum, made by treating the natural 
phosphates with acid, is called by the 
various names of superphosphate, sol- 



uble phosphate, acid phosphate, acid- 
ulated rock, etc. For its manufacture 
the rock phosphates are generally em- 
ployed both because they are cheaper 
and because the organic matter in the 
bones interferes with the use of suffi- 
cient acid to make all the phosphate 
soluble. A good sample of superphos- 
phate or acidulated rock contains 
about IG per cent of phosphoric acid 
in a form that is soluble in water. 

Sometimes when insufficient acid 
has been used a part of the soluble 
phosphate will change into a form in- 
termediate in solubility between the 
natural phosphate and the acid phos- 
phate, and the phosphate is said to 
have undergone "reversion" and the 
new compound is called "reverted 
phosphate." The latter product is sup- 
posed to be more available to the plant 
than the insoluble or natural phos- 
phate, hence the soluble and reverted 
phosphoric acid taken together are 
known as the "available phosphoric 
acid." 

In some instances bone meal is 
treated with a limited amount of sul- 
phuric acid, and the product is called 
"acidulated bone." This substance 
contains a much smaller proportion of 
its phosphoric acid in the soluble form 
than does the rock superphosphate. 
When soluble phosphates are added to 
the soil they soon combine with the 
mineral matter and are converted first 
into the reverted phosphate and finally 
into the insoluble form such as la 
found naturally in the soil. In this 
was the phosphoric acid is "fixed" and 
there is no danger of its being lost 
by leaching. 

(65) Relative Value of Phosphate 
Fertilizers. — The soluble phosphate, 
present in the acidulated goods, is gen- 
erally considered the most valuable 
form of phosphoric acid for use as a 
fertilizer. At first sight it seems use- 
less to go to the expense of making 
the phosphate soluble when it is again 
rendered insoluble by the soil before 
the plant can make use of it. The 
real object in making it soluble is to 
aid in its distribution in the soli. 
When an insoluble phosphate is ap- 
plied it remains where it falls except 
for the slight distribution it receives 
by cultivation. In the case of the solu- 
ble phosphate, on the other hand, the 
phosphate dissolves in the soil water 
and is widely distributed before it 
becomes fixed by the soil. In the for- 
mer case the roots must go to the 



phosphate, while in the latter the 
phosphate is carried to the roots. It 
follows from what has been said that 
after the soluble phosphate is distrib- 
uted throughout the soil the individual 
particles must be very much smaller 
than is the case witk the insoluble 
phosphate, and the importance of fine- 
ness of division has been clearly 
shown. (See 34). 

There are some soils on which super- 
phosphates cannot be used without 
injury, and these are usually soils 
that are deficient in lime; the super- 
phosphate in such cases having a ten- 
dency to make the soils acid. Indeed 
it is asserted that even soils contain- 
ing an abundance of lime in the begin- 
ning may be made acid by the contin- 
ued use of superphosphate if no lime 
is added. 

When the natural phosphates alone 
are considered there is no doubt that 
the preference should be given to 
those derived from bones. The or- 
ganic matter present in the bones de- 
cays when it is incorporated with the 
soil, and this process doubtless causes 
the phosphate to become more readily 
available to the plant, while the rock 
phosphate, on the contrary, is very 
slowly decomposed. At the present 
price of steamed bone meal it is prob- 
ably one of the cheapest substances 
with which to supply phosphoric acid 
where everything is taken into con- 
sideration. 

The use of ground rock phosphate 
or "floats" has not met with general 
favor, and it probably does not give 
good results when used alone. Inves- 
tigations carried on at the Ohio Ex- 
periment Station indicate that when 
added to manure, "floats" have a high 
fertilizing value, in fact the increase 
due to adding the ground rock phos- 
phate to stall manure was quite as 
large as that obtained from the addi- 
tion of superphosphate. It would seem 
from these experiments that the com- 
paratively inexpensive floats might, 
partially at least, replace superphos- 
pnates if used in connection with ma- 
nure, and it is recommended in Bulle- 
tin 134 that the ground rock be used 
"as an absorbent in the stables, thus 
securing an intimate mixture with the 
manure in its fresh condition." 

(66) Complete Fertilizers. — Men- 
tion was made of the fact that the 
basic materials described in the fore-, 
going sections contain only one, or at 
most two, of tne essential elements 
of fertility. Nearly all of the commer- 



cial fertilizers used by the farmers in 
this country are purchased in the form 
known as "complete fertilizers." A 
"complete fertilizer" in the sense In 
which the word is used in trade is one 
that contains nitrogen, phosphoric acid 
and potash and in proportions that are 
supopsed to be suited to the require- 
ments of farm practices. Practically 
all of these fertilizers are made by 
mixing two or more of the basic ma- 
terials heretofore described, the dif- 
ferent ingredients being so combined 
as to give the desired per cent of nitro- 
gen, phosphoric acid and potash. In 
case the basic materials alone yield a 
product that is richer in the essential 
ingredients than is desired by thA 
manufacturer, sufficient sand, gyp- 
sum, dry earth, or other inert matter 
is added to bring the per cent of these 
ingredients down to the desired point. 
These fertilizers are indiscriminately 
rcommended for general use and all 
sorts of startling claims are made for 
them by the various manufacturers. 
They are offered as universal fertiliz- 
ers irrespective of the weii-known fact 
that soils differ widely in their char- 
acteristics, and that the crops vary 
in their food requirements. To be 
sure such a fertilizer, if sufficiently 
rich in nitrogen, phosphoric acid and 
potash, might be made to produce a 
large yield on any kind of a soil if 
used in large quantities, but such a 
use of a fertilizer would result in add- 
ing some of the elements at least in 
quantities far in excess of the need 
of the crop. "Economy requires that 
fertilizers should be adapted to the 
soil and the crop, and that we apply 
only what is needed. Farming is not 
sufl^ciently profitable to make it ex- 
pedient to go on applying elements of 
plant food in excess of what is useful. 
In view of these considerations it is 
evident that the general fertilizers can 
suit only those who are brain lazy — 
those who do not care to study and 
think. No thinking farmer can be sat- 
isfied to blindly and thoughtlessly con- 
tinue the 'hit or miss' system of using 
general fertilizers." (Brooks). 

(67) Special Fertilizers. — A large 
number of so-called special fertilizers 
are now offered by the manufacturers, 
which are supposed to be adapted to 
the particular needs of a special crop 
or class of crops. Each fertilizer gen- 
erally bears the name of the partic- 
ular crop for which it is designed. 
Such fertilizers are offered for all of 
the prominent crops, and there are 



54 



found on the market "corn specials," 
"tobacco specials," "potato specials," 
"truckers' favorite," etc., etc., every 
manufacturer offering a number of 
such products. 

If such fertilizers were compounded 
with any regard to the requirements 
of the particular crop for which they 
were advocated, their use would be a 
distinct advance over the use of the 
general complete fertilizers. Unfor- 
tunately their chief charm is in their 
attractive names, and tueir composi- 
tion is in no way in accord with what 
scientific investigation has shown to 
be necessary for the crop. That these 
mixtures are not based on any scien- 
tific knowledge of the needs of the 
plant is shown by the fact that the 
"specials" offered for the same crop 
by the different manufacturers vary 
as widely in composition as do the 
fertilizers offered for different classes 
of crops. Yet these several makers 
are all claiming to have the best fer- 
tilizers for that particular crop. 

Even were this idea of special fer- 
tilizers for each crop carried out con- 
sistently, it does not take into account 
the fact that soils are very different in 
their fertilizer requirements for the 
same crop, and that a given crop, for 
instance, may fail in one place for lack 
of nitrogen, while the failure in an- 
other case may result from an insuf- 
fiicient supply of phosphoric acid or 
potash. 

"The use of these special fertilizers 
hinders progress. The system is in 
some respects similar to that of quack 
medicines. The farmer calls for a 
specific just as the ignorant or unwise 
patient calls for a quack medicine, and 
just as the intelligent physician, who 
studies the individual peculiarities and 
condition of the patient, can select 
and use medicine with better results 
than can be obtained with any so- 
called specific, so the intelligent 
farmer who will study the peculiari- 
ties and condition of his soils and the 
special needs of his crops can do bet- 
ter than the one who blindly uses 
some special fertilizer which is recom- 
mended to him." (Brooks). 

(68) High and Low-Grade Fertiliz- 
ers. — As the basic materials show 
great variation in the amounts of fer- 
tilizing ingredients they contain, it 
will readily be seen that products 
made by mixing these materials will 
contain very different percentages of 
nitrogen, phosphoric acid and potash. 



If dried blood, steamed bone meal and 
muriate of potash were used, for in- 
stance, the fertilizer would have a 
high content of the three essential ele- 
ments, while if low grade tankage and 
wood ashes or kainite were employed, 
the product would have a much lower 
percentage of the three named sub- 
stances. The use of a filler as well 
makes it possible to have an almost 
endless variety in the composition of 
fertilizers, and hundreds of different 
brands are offered in the market. It 
is customary to designate those hav- 
ing large amounts of plant food as 
"high-grade goods" and those low in 
plant food as "low grade.' While no 
hard and fast line can L.e drawn be- 
tween high and low-grade goods, it 
may be said that any complete fertil- 
izer that contains less than two per 
cent of nitrogen should be considered 
low grade. 

The terms "high grade" and "low 
grade" are used by some writers to 
distinguish the condition of the plant 
food in the fertilizer and not the 
amount. Leather meal, therefore, 
would be classed as low grade because 
the nitrogen in it is in an unavailable 
form, although the amount is rela- 
tively high. It may be stated as a 
general rule that the fertilizers con- 
taining the largest amounts of plant 
food usually have it in the most de- 
sirable condition while the materials 
containing the "toughest" forms of 
plant food are used to make the cheap- 
er fertilizers. 

(69) The Expensivencss of Cheap 
Fertilizers. — A large part of the com- 
mercial fertilizers used by the farmers 
at the present time is purchased in 
the form of cheap mixed or complete 
fertilizers. The low price per ton is 
attractive and, as a "fertilizer is a 
fertilizer" to many people, irrespective 
of its composition, this class of goods 
is sold more readily than those higher 
in price, although the plant food in 
the cheap fertilizers actually cost 
more per pound. This fact is very 
clearly set forth in a recent bulletin 
of the New York Experiment Station, 
from which the table following has 
been adapted. The analyses of all the 
fertilizers sold in the State have been 
compiled along with the retail prices 
and from these data the price per 
pound paid for nitrogen, phosphoric 
acid and potash in the different grades 
of goods has been calculated. The fer- 
tilizers have been divided into four 



LofC. 



classes as follows: Low grade, hav- 
ing a commercial valuation of less 
than sixteen dollars per ton; medium 
grade from sixteen to twenty dollars; 
medium high grade, twenty to twenty- 
five dollars; high grade, over twenty- 
five. For the sake of comparison a 
few of the basic materials are in- 
cluded in the table: 

AvEKAGE Cost of One Pound of Plant 
Food to Consumers. 





Nitrogren 


Phos. Acid 


Potash 




cents 


cents 


cents 


Low Grade Com- 








plete Fertilizers. 


26.3 


8.0 


6.8 


Med. Grade Com- 








plete Fertilizers. 


23.2 


7.0 


6.0 


Med. Hiu'b Gr;)de 








Com. Fertilizers. 


21.0 


6.4 


5.4 


Hiffh Grade Com- 








plete Fertilizers. 


19.6 


6.0 


5.0 




18.5 
14.9 






Bone Meal 


3.96 




Nitrate of Soda. . . 


13.9 






Acid Phosphate. . 




5.1 




Sulphate Potash 






5.0 


Muriate Potash . . 






4.6 



It will be seen that the price per 
pound of plant food is very much less 
in the high-grade goods than in the 
low grade. If the fertilizer is to be 
shipped any distance there is an- 
other point in favor of the high-grade 
goods, for it costs no more for freight 
on a ton of a high-priced fertilizer 
than on a ton of a low-priced one, 
while the former may contain twice 
as much plant food as the latter. 

(70) Home Mixad Fertilizers. — The 
above table not only shows that plant 
food is cheaper in high-grade fertiliz- 
ers than in low grade, but also that 
the essential elements can be pur- 
chased more cheaply in the basic ma- 
terials than in any mixed fertilizer. 
This is due to the fact that the manu- 
facturer must be paid for mixing, bag- 
ging, etc., and Voorhees has shown 
by careful investigations that the aver- 
age charges of the manufacturer for 
this work amounts to $8.50 per ton. 

In other words, the plant food in 
one ton of a mixed fertilizer can be 
purchased by the farmer for from six 
to ten dollars less in unmixed mate- 
rials. This fact suggests the thought 
that it might be possible for the 
farmer to buy the basic materials and 
prepare his own mixed fertilizers. The 
matter of home mixtures has been 
carefully studied by a number of ex- 
periment stations and it has been 
shov/n conclusively that the materials 
can be evenly mixed on the farm, that 



the mechanical condition is good and 
that the results obtained from their 
use are entirely satisfactory. It would 
not be advisable to try to make the 
superphosphate on the farm, but the 
plain acid phosphate can be purchased 
to mix with the other materials. There 
are some obvious advantages other 
than cheapness in home mixing over 
the purchase of mixed fertilizers. The 
usual analysis of a mixed fertilizer 
gives no clew as to the condition or 
source of the nitrogen, and it is diffi- 
cult to determine its availability, while 
in the home-made mixture the condi- 
tion of the nitrogen should always be 
known. Home mixing permits the 
uniting of the different elements in 
the proportions which have been found 
to best meet the requirements of the 
crop and the soil on which it is to be 
raised, something that is not easily 
managed with factory mixed fertiliz- 
ers. By buying the basic materials 
separately it is possible to apply the 
different elements at different times, 
a point that is sometimes of great ad- 
vantage in feeding a crop, especially 
if it is one that needs large quantities 
of nitrogen. In fact the only advan- 
tage that can consistently be claimed 
for the mixed goods is that they are 
more generally aistributed in the mar- 
ket than the basic materials, and can, 
therefore, be more easily purchased 
in such amounts and at such times 
as are convenient. 

The following directions for home 
mixing are taken from a bulletin of 
the Rhode Island Experiment Station 
and are given after a careful inves- 
tigation of the value of home mix- 
tures: 

"In fertilizer factories where the 
business is conducted on a large scale, 
machines are employed which are so 
constructed as to mix considerable 
quantities at a time, and do it rap- 
idly. The conditions existing upon the 
majority of farms are such that an 
elaborate arrangement, even for mix- 
ing small quantities at a time, will not 
be brought into use, and a tight barn 
floor and square pointed shovel will 
be the only requisites at disposal. 
Under such circumstances after weigh- 
ing out the quantities to be mixed 
they should be spread upon the floor 
in layers one upon the other. Then 
beginning at one side and working 
across, the whole should be shoveled 
over; this may be leveled somewhat 
and the operation repeated until the 
mixing is satisfactory. In addition to 



56 



the shovel and the barn floor a large 
screen such as is used in screening 
gravel or coal ashes, may be employed 
with decided advantage; the material 
at the first mixing can be thrown upon 
the screen, and by this means lumps 
may be separated and more easily 
broken up and the thoroughness of the 
mixing will be increased. It may be 
desirable to employ the screen as an 
aid to the mixing even in the subse- 
quent shoveling over, to which the 
material is subjected. Owing to pos- 
sible losses of nitrogen and frequently 
to undesirable changes in the form of 
the phosphoric acid, it is usually not 
advisable to mix the material long be- 
fore using." 

(71). Fertilizer Laws and Guaran- 
tees. — It is impossible for the farmer 
to determine the kind and proportion 
of the different materials entering 
into the composition of a fertilizer by 
its appearance, weight, smell or any 
other physical examination. For- 
merly all commercial fertilizers were 
sold without any guarantee of their 
composition, and the injustice done to 
the purchaser under such a system 
has resulted in the passage of laws 
in most of the states in the Union 
which require the manufacturer or 
dealer to state the actual amounts o'' 
Ihe different constituents contained in 
tliese products. The manufacturers 
are compelled to guarantee the per 
cent of nitrogen (or ammonia), avail- 
able phosphoric acid and potash, that 
each brand contains and usually the 
composition must be stated on each 
bag or parcel of the fertilizer that is 
offered for sale. The enforcement of 
this law, and the chemical examina- 
tion of the fertilizers to determine if 
they agree with the guarantee, are en- 
trusted to the experiment stations in 
some states, while in others they are 
in the hands of the Board of Agri- 
culture. The results of the analyses 
of the various brands are published 
in bulletins for free distribution and 
should be generally consulted by the 
farmers using fertilizers. One result 
of the fertilizer laws has been to 
greatly reduce the number of brands 
offered for sale, and the decrease has 
fallen in a great measure on the low- 
grade goods, as the worthlessness of 
a large number of such brands has 
been exposed by chemical analysis. 

(72) Buying Commercial Fertiliz- 
ers. — In buying fertilizers, as in the 
purchase of other commodities it is 



desirable to get the highest possible 
return for the money invested. It has 
been pointed out that more plant food 
can be obtained for the money in the 
unmixed basic materials than in any 
kind of mixed fertilizers, but in spite 
of this fact there are undoubtedly 
large numbers of persons who will 
continue to buy mixed goods for years 
to come. The attention of such per- 
sons is again called to data given In 
section (69). Whatever form of fer- 
tilizer is used it should be purchased 
only on the basis of its analysis as 
shown by the bulletin from the control 
laboratory, or, in case this is impos- 
sible, on the basis of the lowest 
amounts of nitrogen (or ammonia), 
phosphoric acid and potash which it is 
guaranteed to contain. In many states 
the bulletins referred to give, in addi- 
tion to the analysis, the "calculated 
trade value" or "commercial valua- 
tion." This in most instances repre- 
sents what would be the actual cost 
of the amount of the three valuable 
ingredients of the fertilizer if they 
were purchased for their average re- 
tail trade price. Where such a table 
is available the farmer will do well to 
consult it before making his purchase, 
and in general terms il may be said 
that he should never pay for a mixed 
fertilizer very much in excess of the 
price per ton given in the commercial 
valuation. In case such a table is not 
at hand, the commercial valuation can 
be determined by finding the number 
of pounds of each essential ingredi- 
ent as shown by the guaranteed analy- 
sis, multiplying these by their trade 
values per pound previously given (see 
note under 41) and adding together 
the amounts so determined. It should 
be stated here that the fertilizer guar- 
antees generally contain many more 
statements than are required by law, 
and some of these are apparently 
added to confuse the buyer. In study- 
ing a guarantee of a mixed fertilizer it 
should constantly be kept in mind 
that the only statements of interest to 
the purchaser are the per cents of 
nitrogen (or amomnia), available 
phosphoric acid and potash, and that 
all others should be ignored. The law 
requires these to be given, so they can 
always be found in the guarantee. 
Some states require the per cent of 
nitrogen to be stated, while others 
allow it to be given as ammonia, which 
is about four-fifths nitrogen. The 
potash is sometimes stated as "actual 



57 



potash," but in any case the buyer 
must not allow himself to be confused 
by statements of equivalents of bone 
phosphate, sulphate of potash, etc., 
but must shut his eyes to everything 
except the lowest guaranteed per cent 
of the three essential ingredients. A 
simple method which will give very 
nearly the commercial valuation of a 
fertilizer is to multiply the per cent 
of nitrogen by three, add the product 
to the per cents of available phos- 
phoric acid and potash and the result 
will be the commercial value of a ton 
of the fertilizer in dollars and cents. 

Example: Supose a fertilizer is 
guaranteed to contain 2.4% of nitro- 
gen, 10.5% of available phosphoric 
acid and 4.0% of potash. Multiplying 
2.4 by 3 gives 7.2. To this add 10.5 
and 4.0 and the result is 21.7, which 
means that the commercial valuation 
is $21.70 per ton. In case the analysis 
states ammonia instead of nitrogen, 
the ammonia should be multiplied by 
2% and added to the available phos- 
phoric acid and potash. The valuation 
determined in this way should be com- 
pared with the selling price of the fer- 
tilizer and the difference should never 
exceed five dollars per ton. Taking 
the precaution to compare the com- 
mercial valuation and the selling price 
it is always wise to purchase high- 
grade fertilizers. Money can gener- 
ally be saved by co-operative buying, 
for the price per ton is generally less 
in quantities and the freight charges 
are reduced. 

(73) Trade .Values Not Agricul- 
tural Values. — The values for commer- 
cial fertilizers and manure which have 
been discussed are trade values and 
do not necessarily bear any relation to 
the agricultural value of these sub- 
stances. Trade values are determined 
by the law of supply and demand, and 
many of the materials used in commer- 
cial fertilizers are required by other 
industries as well, so it is not the agri- 
cultural demand alone that sets the 
price. The agricultural value of a fer- 
tilizer is measured by the value of the 
increased crop produced by its use and 
is, therefore, a variable factor depend- 
ing upon the availability of its con- 
stituents and the character of the crop 
to be raised. It is possible to have 
circumstances under which a fertilizer 
with a comparatively low commercial 
valuation may have a high agricul- 
tural value. 



(74) Using Commercial Fertilizers. 

— From what has already been said it 
will be evident to the reader that the 
fertilizer to be used depends on the 
soil and on the crop to be raised. A 
complete study of the use of commer- 
cial fertilizers would call for separate 
treatment of each crop and its require- 
ments, but such a discussion would 
demand much more space than is con- 
sistent with the original conception 
of this series of articles. This treatise 
was intended to deal with the princi- 
ples underlying farm practice rather 
than with the practice itself, and for 
that reason only general principles 
will be taken up in this connection. 

Commercial fertilizers have been on 
the market for a sufficient length of 
time to have been widely used, and 
as might have been surmised, there 
have been developed a number of dif- 
ferent plans or sytems for their use 
which vary somewhat in the princi- 
ples on which they are based, and 
which will be briefly discussed. 

"The one which has perhaps re- 
ceived the most attention, doubtless 
largely because one of the first pre- 
sented, and in a very attractive man- 
ner, is the system advocated by the 
celebrated French scientist, George 
Ville. This system, while not to be 
depended upon absolutely, suggests 
Imes of practice which, under proper 
restrictions, may be of very great ser- 
vice. In brief, this method assumes 
that plants may be, so far as their 
fertilization is concerned, divided into 
three distinct groups. One group is 
specifically benefited by nitrogenous 
fertilization, the second by phosphatic, 
and the third by potassic. That is, in 
each class or group, one element more 
than any other rules or dominates the 
growth of that group, and hence each 
particular element should be applied 
in excess to the class of plants for 
which it is a dominant igredient. In 
this system it is asserted that nitrogen 
i^; the dominant ingredient for wheat, 
rye, oats, barley, meadow grass and 
beet crops. Phosphoric acid is the 
dominant fertilizer ingredient for tur- 
nips, Swedes, Indian corn (maize), 
sorghum and sugar cane; and potash 
is the dominant or ruling element for 
peas, beans, clover, vetches, flax and 
potatoes. It must not be understood 
that this system advocates only single 
elements, for the others are quite as 
important up to a certain point, be- 
yond which they do not exercise a con- 



trolling influence in the manures for 
the crops of the three classes. This 
special or dominating element is used 
in greater proportion than the others, 
and if soils are in a high state of cul- 
tivation, or have been manured with 
natural products, as stable manure, 
they may be used singly to force a 
maximum growth of the crop. Thus, 
a specific fertilization is arranged for 
the various rotations, the crop receiv- 
ing that which is the most useful. 
There is no doubt that there is a good 
scientific basis for this system, and 
that it will work well, particularly 
where there is a reasonable abundance 
of all the plant food constituents, and 
where the mechanical and physical 
qualities of soil are good, though its 
best use is in "intensive" systems of 
practice. It cannot be depended upon 
to give good results where the land 
is naturally poor, or run down, and 
where the physical character also 
needs improvement. 

"Another system which has been 
urged, notably by German scientists, 
is based upon the fact that the min- 
eral constituents, phosphoric acid and 
potash, form fixed compounds in the 
soil, and are, therefore, not likely to 
be leached out, provided the land is 
continuously cropped. They remain in 
the soil until used by growing plants, 
while the nitrogen, on the other hand, 
since it forms no fixed compounds and 
is perfectly soluble when in a form 
useful to plants, is liable to loss from 
leaching. Furthermore, the mineral 
elements are relatively cheap, while 
the nitrogen is relatively expensive, 
and the economical use of this expen- 
sive element, nitrogen, is dependent to 
a large degree upon the abundance of 
the mineral elements in the soil. It is, 
threfore, advocated that for all crops 
and for all soils that are in a good 
state of cultivation, a reasonable ex- 
cess of phosphoric acid and potash 
shall be applied, sufiicient to more 
than satisfy the maximum needs of 
any crop, and that the nitrogen be 
applied in active forms, as nitrate or 
ammonia, and in such quantities and 
at such times as will insure the mini- 
mum loss of the element and the max- 
imum development of the plant. The 
supply of the mineral elements may 
be drawn from the cheaper materials, 
as ground bone, tankage, ground phos- 
phates and iron phosphates, as their 
tendency is to improve in character; 
potash may come from the crude salts. 
Nitrogen should be applied as nitrate 



of soda, because in this form it is 
immediately useful, and thus may be 
applied in fractional amounts, and at 
such times as to best meet the needs 
of the plant at its different stages of 
growth, with a reasonable certainty of 
a maximum use by the plants. Thus 
no unknown conditions of availability 
are involved, and when the nitrogen 
is so applied, the danger of loss by 
leaching, which would exist if it were 
all applied at one time, is obviated." 
(Voorhees). 

Still another system is based on the 
food requirements of the plant as 
shown by the analysis of the plant 
itself. The amount of plant food re- 
moved from each acre of ground is 
calculated from the analysis of the 
plant and a corresponding amount is 
returned to the soil. Different for- 
mulas are, therefore, recommended for 
each crop, and in these the nitrogen, 
phosphoric acid and potash are com- 
bined in the same proportions in 
which they are found in the plant. 
Experience shows that it is necessary 
to add amounts of these fertilizers to 
the soil that will supply more plant 
food than is removed by the crop if 
the maximum results are desired. 
This system may result in a large 
yield, but cannot be considered an 
economical method of feeding the 
plant, as one or more of the elements 
is likely to be applied in excess of 
the requirements of the crop. It does 
not take into consideration, for in- 
stance, the fact that a plant which con- 
tains a large amount of one element 
of plant food may possess unusually 
great power of procuring that element 
from the soil. The principle underly- 
ing this system, of course, is the idea 
that to maintain the fertility of the 
soil unimpaired an amount of plant 
food equivalent to that removed by 
the crop must be returned to the land. 
To this extent the system is similar 
to the use of barnyard manure, but 
is not so effective. 

Another system used in ordinary or 
"extensive" farming is to apply all 
the fertilizer to the "money crop" in 
a rotation. This method is used espe- 
cially where only one crop in a rota- 
tion is sold, the others being fed on 
the farm. A liberal supply of food 
is used to give the maximum yield 
which the climate and season will per- 
mit. The amount of food applied is 
in excess of the requirements of the 
crop and the residue is depended upon 
to help nourish the succeeding crops. 



59 



or at least the one immediately suc- 
ceeding the money crop. This system 
has some valuable features and is 
probably the one most in use in this 
country at the present time. 

Too frequently fertilizers are used, 
by what certain writers have called 
the "hit or miss" system. No special 
thought is given to the requirements 
of the crop or the composition of the 
fertilizer, but if the farmer feels that 
he can afford it and the agent is a 
glib talker, the sale is made. If the 
buyer happens to "hit" the food re- 
quirements of his crop a profit is se- 
cured and he is correspondingly 
happy, while if he makes a "miss" he 
feels assured that there is no value 
in commercial fertilizers. 

All of these systems, with the ex- 
ception of the last one mentioned, 
have their good features and have 
proven remunerative in the hands of 
many of their advocates. They all 
have, however, one weak point in com- 
mon, i. e., they do not take into con- 
sideration the fact that different soils 
contain varying amounts and propor- 
tions of plant food and that while a 
certain soil may be lacking in potash, 
for instance, it may contain amounts 
of nitrogen and phosphoric acid suf- 
ficient for a maximum yield. Such a 
soil would obviously be benefited by 
an application of potash, while nitro- 
gen and phosphoric acid would pro- 
duce no effect. Experiments have 
shown that on ordinary soils it sel- 
dom happens that all three of the ele- 
ments of fertility are required at one 
time. Unfortunately there is no easy 
way of determining accurately the fer- 
tilizer requirements of a soil for a 
particular crop. Van Slyke has for- 
mulated the following general rules 
which may be of value where no accur- 
ate data is at hand. 

"It is impossible to give any fixed 
rules which will cover all cases and 
enable a farmer to tell without any 
experiment on his part what food con- 
stituents his soil lacks. In a general 
way, the crops themselves may give 
some valuable suggestions. 

(a) As a rule, lack of nitrogen is 
indicated, when plants are pale-green, 
or when there is small growth of leaf 
or stalk, other conditions being favor- 
able. 

(b) A bright, deep-green color, with 
a vigorous growth of leaf or stalk, is, 
in case of most crops, a sign that nitro- 



gen is not lacking, but does not neces- 
sarily indicate that more nitrogen 
could not be used to advantage. 

(c) An excessive growth of leaf or 
stalk, accompanied by an imperfect 
bud, flower, and fruit development, in- 
dicates too much nitrogen for the 
potash and phosphoric acid present. 

(d) When such crops as corn, cab- 
bage, grass, potatoes, etc., have a lux- 
uriant, healthful growth, an abundance 
of potash in the soil is indicated; also, 
when fleshy fruits of fine flavor and 
texture can be successfully grown. 

(e) When a soil produces good, 
early maturing crops of grain, with 
plump and heavy kernels, phosphoric 
acid will not generally be found defi- 
cient in the soil. 

"Such general indications may often 
be most helpful, and crops should be 
studied carefully with these facts in 
mind. 

"In order to ascertain with greater 
certainty what food elements are lack- 
ing in the soil, the surest way is for 
each farmer to do some experimenting 
on his own soil and crops. Apply 
different kinds of fertilizing materials 
in different combinations, using for 
example, potash compounds alone in 
one place, phosphoric acid compounds 
in another, nitrogenous materials in 
another. Then different combinations 
can be made on other portions of the 
crop. Some portions of the field can 
be left without application of any kind. 
The results can then be studied in 
the yield of crop. It is generally 
found that the application of phos- 
phoric acid gives excellent results on 
fields which have long been cropped 
with grain without keeping up the sup- 
ply of plant food. In other places, it 
is found that best results are obtained 
with application of potash compounds. 
And many cases require a liberal sup- 
ply of all three forms of plant food. 
In carrying on such field tests several 
difficulties may be met. The season 
may frequently be such as to interfere 
seriously with the favorable action of 
the fertilizing materials applied. Thus 
a serious drouth may counteract all 
other conditions and prevent a satis- 
factory yield. The difference of me- 
chanical condition of the soil on the 
same farm or even in the same field 
may prevent a fair comparison of the 
action of different kinds of fertilizing 
materials and elements. But, notwith- 



60 



standing such difficulties, valuable 
suggestions will be gained from an ex- 
perimental study of one's soils through 
the behavior of the crops." 

This method of determining the fer- 
tilizing material which must be added 
to the soil is, in the opinion of the 
writer, the only rational system and 
the only one that can be depended 
upon for consistent results. 

(75) Commercial Fertilizers Not 
All-Sufficient. — Absolute dependence 
should not be placed on commercial 
fertilizers alone to maintain the fertil- 
ity of the soil. Their continued appli- 
cation without the use of any other 
method of improving the soil will 
eventually result in serious injury to 
its physical condition. Commercial 
fertilizers add litlte or no humus to 
the soil, and to obtain the best results 
it is absolutely necessary to provide 
humus, either by plowing under green 
crops or by the use of barnyard ma- 
nure. Numerous experiments have 
shown that commercial fertilizers give 
much better returns when used in con- 
nection with barnyard manure than if 
used alone, and they are coming to be 
used in this manner more and more 
as the subject is more thoroughly in- 
vestigated. 

It may be said here that commercial 
fertilizers are not merely "stimulants" 
as is frequently imagined, but that 
they actually supply plant food, and if 
rationally used will leave the soil more 
fertile than before their use instead 
of decreasing its fertility as would be 
likely to happen if a mere stimulant 
were used. Commercial fertilizers 
have an important place in the rural 
economy, but they should not be used 
to do the work that can be betetr ac- 
complished by properly husbanding 
the home resources. 

(76) Soil Amendments. — There are 
various substances that are beneficial 
to the land under some conditions al- 
though they add neither humus nor 
important quantities of plant food. 
Such substances have been called "soil 
amendments' and the benefit from 
their use arises from the fact that 
they produce certain changes in the 
soil which directly or indirectly pro- 
mote plant growth. Some of them 
contain small amounts of plant food, 
but their value is chiefly due to their 
secondary eflfect on the soil and not 
that they add nitrogen, phosphoric 
acid or potash. LIME is probably 



the most important substance of this 
class and its use as a manure ante- 
dates the Christian era. Although 
lime has been einployed as a fertilizer 
for so long a time it is only in recent 
years that its action has been ex- 
plained, and at the present time there 
remain for investigation many ques- 
tions concerning the action of lime 
on the soil. 

In a few instances lime has a di- 
rect manurial value, for occasionally 
a soil is found which is so lacking 
in this substance that the crops are 
unable to obtain sufficient lime for 
a maximum yield. Such soils are 
rare, and in nearly every instance the 
good results from the use of lime are 
due to its indirect eflfect. The efifects 
of lime may be considered to be of 
three kinds, i. e., mechanical, chem- 
ical and biological. 

Lime has a very marked effect on 
the mechanical condition of the soil. 
When added to sandy soil it tends 
to make it more compact by partially 
cementing together the particles of 
sand and makes the soil capable of 
retaining larger quantities of water. 
When used on clay lands, on the 
other hand, lime makes the soil more 
mellow. A clay soil containing very 
little lime is made fine with greatest 
difficulty; it adheres to the imple- 
ments used when wet, and cracks 
when allowed to dry. A soil rich 
in lime crumbles more easily, is read- 
ily brought into good tilth and does 
not adhere to any appreciable extent 
to the implements. The addition of 
lime to a soil containing much clay 
makes the soil more friable, and 
makes it possible for the rains to per- 
colate more easily through the soil, 
and overcomes the danger of "pud- 
dling." The puddling of clay soils 
is due to the fact that the clay is com- 
posed of very small granules which 
fit so closely together that the water 
cannot pass between. When lime is 
added to the soil a number of these 
small particles become cemented to- 
gether to form a much larger granule 
and as the granules increase in size 
the spaces between them also become 
larger. 

Any one can easily satisfy himself 
in regard to this valuable effect of 
lime on stiff clay by taking a sample 
of such clay and working it thor- 
oughly and then allowing it to dry, 
when it becomes as hard as a brick. 
If to another portion of the clay a 
little lime is added (say one-half of 



61 



one per cent) and this is moistened, 
mixed thoroughly and allowed to dry, 
it will be found that a mere touch will 
cause it to crumble to pieces. There 
are other materials that have a some- 
what similar effect on clay, but none 
are so efficient as lime. This granu- 
lated condition of clay soils, so eas- 
ily accomplished by liming, is not 
easily destroyed, but will last for 
some years. 

Lime is useful in making potential 
plant food available. Much of the 
potash of the soil, for instance, is 
locked up in insoluble compounds and 
is not available to the plant. Lime 
may decompose these compounds and 
thereby convert the potash into forms 
that the crop can use. Experiments 
have proven that when lime is ap- 
plied to a soil originally poor in this 
constituent, the plants grown are not 
only richer in lime but also in potash. 
The use of lime then may for a time 
have a similar effect to that of potash 
containing manures, but it must be 
remembered that the lime does not 
supply potash, it merely makes that 
present in the soil available, and if 
the store of potash originally present 
is small it will probably need liberal 
potash manuring at an earlier date 
because of liming. 

Caustic lime acts energetically on 
organic matter and its beneficial ac- 
tion on peaty or other soils contain- 
ing large quantities of undecomposed 
vegetable matter may be partly due 
to this fact. 

Recent investigations have shown 
that many soils fail to produce good 
crops because they are acid or "sour." 
Formerly it was supposed that only 
low lying or marshy land ever be- 
came sour, but experiments conducted 
by the American experiment sta- 
tions have demonstrated that there 
are large areas of uplands which an 
acid condition of the soil exists. 
Acidity of the soil is injurious to 
nearly all of the cultivated crops, so 
that good returns cannot be expected 
from sour lands. Where such a con- 
dition exists the liberal use of lime 
is the proper remedy. Acidity may 
result from a number of causes such 
as the presence of stagnant water, 
turning under of large quantities of 
organic matter, constant use of com- 
mercial fertilizers, etc., but whatever 
the cause, lime is the practical neu- 
tralizer. An acid conditon of the soil 
can sometimes be foretold by obser- 
vation of the character of the plant 



growth thereon. Where such plants 
as the common sorrel, beard grass, 
rushes and mosses grow to the ex- 
clusion of the more desirable plants 
it is a pretty sure indication that 
the soil is acid, for the plants named 
are not injured by acidity while the 
others are. 

Probably the best method of test- 
ing the soil for acidity is what is 
known as the litmus paper test. The 
test is applied as follows: a little of 
the surface soil is scratched aside and 
the piece of litmus paper pressed onto 
the moist soil beneath. If the paper 
turns a reddish color it shows that 
the soil is sour. To obtain good re- 
sults only the best "neutral" litinus 
paper should be used. The state- 
ments so often seen in the agricul- 
tural press about making this test 
are frequently misleading, for most 
of the litmus paper on sale in the 
retail stores is worthless for this pur- 
pose, and those who contemplate 
making the test should be sure to 
obtain a good sample of neutral lit- 
mus paper. An amount of acid that 
would entirely prevent the growth of 
clover, for instance, might not change 
the color of the common litmus pa- 
per at all. The clovers and other 
legumes seem to be especially sen- 
sitive to acid, and in many cases the 
failure of clover has been shown to 
be due to the acidity of the soil. 
In such cases the application of lime 
resulted in a good crop of clover. 

Lime is valuable because it pro- 
motes the growth of the desirable 
bacteria in the soil. It has been 
shown that one of the most impor- 
tant changes in the soil due to bac- 
terial action is the process of nitri- 
fication (14). The nitrifying bacteria 
cannot thrive in a soil that is deficient 
in lime. These bacteria are injured 
by acidity, so it is necessary to keep 
the soil "sweet' to promote their ac- 
tion. On the other hand, the injur- 
ious process of denitrification (15) 
takes place more readily in sour soils, 
so that lime in promoting the desira- 
ble process overcomes the undesirable. 
The bacteria which grow in the 
nodules found on the roots of the 
legumes and which "fix" the nitrogen 
of the air will not perform their func- 
tions in an acid soil, therefore lime 
in keeping the soil sweet promotes 
the gathering of nitrogen by the le- 
guminous plants. In general it may 
be said that all the desirable fermen- 



62 



tations in the soil are accelerated by 
the presence of lime. 

It is generally recommended that 
freshly slaked "burnt" lime be used 
•on heavy clay lands, while air-slaked 
or "mild" (carbonate of lime) or marl 
be applied on sandy soils. As the 
lime is gradually carried downward 
in the soil it should always be ap- 
plied to the surface, and, if possible, 
thoroughly incorporated with the 
upper few inches of the soil. From 
one-half to one and one-half tons 
per acre applied once in five or six 
years is usually sufficient. As in the 
case of commercial fertilizers the best 
way to determine if lime is necessary 
is by the plot test, using some crop 
which is especially benefited by lime. 
It has been said that "lime makes 
the father rich and the son poor," 
and this is undoubtedly true if lime 
is used alone. Lime adds no plant 
food to the soil, but simply brings 
about conditions that enable the crop 
to use large quantities of the store of 
food already present in the soil, so 
that if used alone it only makes the 
exhaustion of the soil take place more 
rapidly. It has, however, a legiti- 
mate place in agriculture, and if used 
in connection with green crops, barn- 
yard manure and commercial fertiliz- 
ers will produce only beneficial re- 
sults. Large quantities of lime should 
not be applied immediately before a 
crop of potatoes, as it has a tendency 
to cause the production of scabby 
tubers. 

MARL is mild lime (carbonate of 
lime) in the form of a fine powder, 
and is found in some parts of the 
country in large deposits. It has the 
same efifect on the soil that air-slaked 
lime has and is a very convenient 
form in which to apply to sandy soils. 
Some of the European marls contain 
appreciable quantities of potash and 
phosphoric acid as well, but the 
American marls are of value only for 
the lime they contain. 

GYPSUM or land plaster is a com- 
pound of lime with sulphuric acid 
(sulphate of lime) and has been used 
for many years as a fertilizer. For 
a long time the action of land plaster 



was little understood, but it is now 
generally believed that its beneficial 
action is due to the fact that the plas- 
ter sets free the unavailable potash 
of the soil, and for this purpose it is 
more useful than lime. It is of value 
to those crops that are benefited by 
the use of potash manures and, as 
will be surmised, plaster gives good 
results only on soils containing large 
amounts of potential potash. For 
this reason it gives best returns when 
used on clay soils and practically no 
beneficial results when used on sandy 
soils. The best method of using it 
is probably to add it to manrue as 
has been suggested (51). When 
gypsum has been used continually it 
has been found that after a time it 
fails to produce satisfactory results. 
In the latter case it is probable that 
the crop would be benefited by an 
application of some potash manure. 
SALT was among the first sub- 
stances to be used as a manure, but 
in spite of the antiquity of its use 
the value of salt as a fertilizer is still 
in dispute. It is certain that injury 
has resulted from the application of 
salt quite as often as benefit, and in 
fact it may be said that there are no 
experiments of any note which indi- 
cate that salt has any beneficial efifect 
on plant growth. Large quantities 
of salt are poisonous to plants, as 
everyone knows, due undoubtedly to 
the chlorine that he salt contains. It 
was formerly supposed that such 
plants as asparagus were benefited by 
the application of salt, but investiga- 
tions have not shown any increase in 
yield from its use. It is well known 
that salt checks fermentations of all 
kinds, so that it probably decreases 
the rate of nitrification which is sel- 
dom desirable. It is said that adding 
salt to the soil will make the straw 
of wheat stiflfer, but this effect is very 
likely due to the fact that the salt 
on acount of its poisonous action 
makes the straw shorter and the 
greater stiffness is due to reduced 
length. Many so-called "agricultural 
salts" are on the market, but they 
certainly do not possess any virtues 
not found in common salt, and it is 
doubtful if there is any manurial value 
in salt of any kind. 



63 



DEC 30 1904 



X 



l.BAp"n5 



